feed.xml

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
  <channel>
    <title>Pixio - Mobile Technology Consulting Services</title>
    <description>Pixio is a team of educators and developers specializing in native mobile development and hardware communication. We have gained a reputation as one of the top mobile technology consulting services.</description>
    <link>http://www.pixio.com/</link>
    <atom:link href="http://www.pixio.com/feed.xml" rel="self" type="application/rss+xml" />
    <pubDate>Tue, 25 Oct 2016 12:50:45 -0600</pubDate>
    <lastBuildDate>Tue, 25 Oct 2016 12:50:45 -0600</lastBuildDate>
    <generator>Jekyll v3.3.0</generator>
    
      <item>
        <title>Battle of the bOStards: Activities vs. View Controllers</title>
        <description>&lt;p&gt;Like most things in life, there is almost always a Game of Thrones (GoT) analogy that can be used to describe it perfectly. In the case of Android vs. iOS there is no better analogy in the GoT universe than the 2016 episode &lt;a href=&quot;http://www.imdb.com/title/tt4283088/?ref_=fn_al_tt_1&quot;&gt;Battle of the Bastards&lt;/a&gt;. For those that do not know what GoT is, or have yet to see the episode, I will give you a brief spoiler-proof overview. The plot line is pretty straightforward, there is a battle between good and evil. Now most you are probably asking yourself, how in the world does a battle between good and evil from a fantasy TV show relate to Android vs. iOS? Pretty much every mobile developer I have ever come across has a predetermined opinion on which mobile platform is better, and in most developer’s eyes, usually one of the platforms is good and the other is pure evil. (Oh, and FYI, if they say that they prefer Windows Phone, run and hide, because only a white walker would support the platform of the living dead).&lt;/p&gt;

&lt;p&gt;The focus of today is Android Activities vs. iOS View Controllers. In this article I will describe what each of these things are, their pros and cons, and provide a small example for each highlighting a few of their features.  Let’s first start with Activities.&lt;/p&gt;

&lt;h4 id=&quot;activities&quot;&gt;Activities:&lt;/h4&gt;

&lt;p&gt;An &lt;a href=&quot;https://developer.android.com/guide/components/activities.html&quot;&gt;Activity&lt;/a&gt; is a single, focused thing that a user can do. This definition might seem very vague and general - that’s because Activities are meant to be general purpose. But while Activities might be able to perform a number of different actions, one thing remains the same: Activities are a crucial part of every Android application. In fact they are so crucial that every single android application is required to have at least one Activity, and oftentimes they are made up of a number of them, unless of course a developer chooses to use fragments, but that is an entirely different subject for another day.
An Activity often acts as the Controller in the Model-View-Controller (MVC) architecture. It is responsible for communicating with the model and determining what information to display to the user.  Beyond their immediate function, they have a complex “life cycle”: the ways in which they are created, displayed, hidden, and destroyed by the system.  This life cycle consists of a number of different methods that are called at different points during the Activities life. Some of these methods include &lt;code&gt;onCreate()&lt;/code&gt;, &lt;code&gt;onResume()&lt;/code&gt;, &lt;code&gt;onStop()&lt;/code&gt; and &lt;code&gt;onDestroy()&lt;/code&gt; just to name a few.  It is crucial for any Android developer to not only know of all these life cycle methods, but to also understand when and why they are called during the activities life cycle.  &lt;/p&gt;

&lt;p&gt;Now that you have had an overview on what an activity is, and a few of its life cycle methods, let’s jump right into an example. In this example we will create a simple activity and demonstrate when a few of its life cycle methods are called.
First let’s start a new Android studio project. You can name your project whatever you like, I chose ActivityExample. Next let’s select the minimum SDk as API 16, start with a blank activity, and leave the activity name as MainActivity. Now that we are all set up let’s see what we have got to work with. If you open the &lt;code&gt;MainActivity.java&lt;/code&gt; file you will see that we have one method in our class, &lt;code&gt;onCreate()&lt;/code&gt;. &lt;code&gt;onCreate()&lt;/code&gt; is crucial to every activity because it specifies what needs to happen when an Activity is created for the first time (think of it as a constructor).  By default the MainActivity is making a call to super and setting a view that will be displayed to the user. This is very typical of an Activity, and most Activities will make at a minimum these two calls in &lt;code&gt;onCreate()&lt;/code&gt;.&lt;/p&gt;

&lt;p&gt;Now run the app. You should see a blank screen with the famous, “Hello World” displayed on it. Now that you have a basic activity up and running, let’s do something useful with it. In Android Studio navigate to the &lt;code&gt;activity_main.xml&lt;/code&gt;layout file in the res/layout folder and open it up. Change the layout to a &lt;code&gt;RelativeLayout&lt;/code&gt; and put an &lt;code&gt;EditText&lt;/code&gt; object in the center of the screen, making sure to change the background color so we can see it. Like so.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-xml&quot; data-lang=&quot;xml&quot;&gt;&lt;span class=&quot;cp&quot;&gt;&amp;lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&amp;gt;&lt;/span&gt;

&lt;span class=&quot;nt&quot;&gt;&amp;lt;RelativeLayout&lt;/span&gt;

    &lt;span class=&quot;na&quot;&gt;android:id=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@+id/activity_main&quot;&lt;/span&gt;

    &lt;span class=&quot;na&quot;&gt;xmlns:android=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;http://schemas.android.com/apk/res/android&quot;&lt;/span&gt;

    &lt;span class=&quot;na&quot;&gt;xmlns:app=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;http://schemas.android.com/apk/res-auto&quot;&lt;/span&gt;

    &lt;span class=&quot;na&quot;&gt;xmlns:tools=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;http://schemas.android.com/tools&quot;&lt;/span&gt;

    &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;

    &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;

    &lt;span class=&quot;na&quot;&gt;tools:context=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;org.com.activityexample.MainActivity&quot;&lt;/span&gt;

    &lt;span class=&quot;na&quot;&gt;android:gravity=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;center&quot;&lt;/span&gt;

    &lt;span class=&quot;na&quot;&gt;android:background=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@android:color/black&quot;&lt;/span&gt;&lt;span class=&quot;nt&quot;&gt;&amp;gt;&lt;/span&gt;

    &lt;span class=&quot;nt&quot;&gt;&amp;lt;EditText&lt;/span&gt;

        &lt;span class=&quot;na&quot;&gt;android:id=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@+id/textbox&quot;&lt;/span&gt;

        &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;300dp&quot;&lt;/span&gt;

        &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;50dp&quot;&lt;/span&gt;

       &lt;span class=&quot;na&quot;&gt;android:background=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@android:color/white&quot;&lt;/span&gt;

        &lt;span class=&quot;nt&quot;&gt;/&amp;gt;&lt;/span&gt;
&lt;span class=&quot;nt&quot;&gt;&amp;lt;/RelativeLayout&amp;gt;&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Now that we have something useful on screen, let’s run the application again and test it out.  Click on the text box and enter in some text. It appears to be working right? Not so fast, let’s see what happens to our text when we rotate the device. Test it out… Poof, your text vanished like Rob Stark during the Red Wedding. So what happened? What evil force stole your text? Any guesses? And no it wasn’t the blood magic of the Red Woman. Instead, your text is no longer alive (in memory) because the Activity that it lived in is no longer alive. But how can the Activity no longer be alive? I can see it on screen with my own two eyes. The reason my friends, is because of the Activity’s life cycle. Every time an Activity is rotated it is destroyed and created again. So any data that was living in the previous activity is destroyed when a call to &lt;code&gt;onDestroy()&lt;/code&gt; is made by the application. Still don’t believe me? Test it out. Override the &lt;code&gt;onDestroy()&lt;/code&gt; method and add a log message to the debug log, and while we are at it let’s also add a log message to the &lt;code&gt;onCreate()&lt;/code&gt; method. Like so.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;protected&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onCreate&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Bundle&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;savedInstanceState&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;onCreate&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;savedInstanceState&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;setContentView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;layout&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;activity_main&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;message&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;What is dead may never die.&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;Log&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;d&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;Debug: &quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;message&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;protected&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onDestroy&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;onDestroy&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;message&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;To be called or not to be called, that is the question.&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;Log&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;d&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;Debug: &quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;message&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Run the application again and rotate the device. Now, if you inspect the Debug log, you will see your messages in the following order: your create message, followed by your destroy message, followed lastly by your create message again. This is because the activity is being created when it first loads, destroyed when the screen is rotated and recreated when the device has finished rotating.&lt;/p&gt;

&lt;p&gt;So how do you persist the data during a rotation? The answer to that also lies in an Activity’s life cycle, but requires a bit of work. The keys are a few of the other life cycle methods, &lt;code&gt;onPause()&lt;/code&gt; and &lt;code&gt;onResume()&lt;/code&gt;. &lt;code&gt;onPause()&lt;/code&gt; is called every time an Activity goes out of scope. So anytime an activity gets removed from the view of a user &lt;code&gt;onPause()&lt;/code&gt; is called.  &lt;code&gt;onResume()&lt;/code&gt; is called anytime an Activity comes back into scope, it is also called immediately after a call to &lt;code&gt;onCreate()&lt;/code&gt;. But just knowing that &lt;code&gt;onPause()&lt;/code&gt; and &lt;code&gt;onResume()&lt;/code&gt; exists is not enough. You need to know how to use it properly in order to persist data.  The quick and dirty way of achieving our goal is simply to write our text to a file in &lt;code&gt;onPause()&lt;/code&gt; and load the data from file in &lt;code&gt;onResume()&lt;/code&gt;. Here is an example of how to accomplish this. Keep in mind that this is the &lt;em&gt;wrong&lt;/em&gt; way of doing this in a proper application. Instead, you would want to use an MVC architecture and store all of the data applicable to your application in a model when the Activity is destroyed and then simply reference that model when the Activity is re-created. This will save you a lot of overhead because you will not have to write to file every time an Activity goes out of scope.  But using a model is an entirely other topic itself, so we will stick to the quick and dirty way for this example.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;protected&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onPause&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;onPause&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;message&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;Stop... hammer time&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;Log&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;d&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;Debug: &quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;message&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//Get the current message&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;currentMessage&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;EditText&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;findViewById&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;textbox&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;))).&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;getText&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;().&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;toString&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//Save the data in the text box to file&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;try&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;OutputStreamWriter&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fileWriter&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;OutputStreamWriter&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;getBaseContext&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;().&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;openFileOutput&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;data.txt&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Context&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;MODE_PRIVATE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;fileWriter&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;write&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;currentMessage&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;fileWriter&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;close&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;catch&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;IOException&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;Log&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;File Save&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;Could not write to the following file: &quot;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;toString&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;());&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;protected&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onResume&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;onResume&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;

    &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;data&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//Load the data from file&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;try&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;InputStream&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;inputStream&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;openFileInput&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;data.txt&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;inputStream&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;InputStreamReader&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fileInputReader&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;InputStreamReader&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;inputStream&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;BufferedReader&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;bufferedFileReader&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;BufferedReader&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;fileInputReader&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;receiveString&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;StringBuilder&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;stringBuilder&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;StringBuilder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;

            &lt;span class=&quot;k&quot;&gt;while&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;receiveString&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;bufferedFileReader&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;readLine&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;())&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
            &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
             &lt;span class=&quot;n&quot;&gt;stringBuilder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;append&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;receiveString&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
            &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

            &lt;span class=&quot;n&quot;&gt;inputStream&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;close&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;data&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;stringBuilder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;toString&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;catch&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;FileNotFoundException&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;Log&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;File Loader&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;Could not find the file: &quot;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;toString&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;());&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;catch&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;IOException&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;Log&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;File Loader&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;Can not read file: &quot;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;e&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;toString&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;());&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//write the message back into the text box&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;EditText&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;textBox&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;EditText&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;findViewById&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;textbox&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;textBox&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;setText&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;data&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;toCharArray&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(),&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;data&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;toCharArray&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;().&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;length&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Congratulations! Your text now persists through device rotation. At this point you are probably despising Android. I mean how can something so simple be so difficult? Well my friends, it’s not. I’m going to fill you in on a little secret and you are probably going to hate me after having done all that file work. Go ahead and comment out the &lt;code&gt;onPause()&lt;/code&gt; and &lt;code&gt;onResume()&lt;/code&gt; methods and add the following line of code to the EditText attribute in &lt;code&gt;activity_main.xml&lt;/code&gt;.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-xml&quot; data-lang=&quot;xml&quot;&gt;android:freezesText=&quot;true&quot;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Now run your application again and test out rotation. See, I told you that you were going to hate me. So if you could fix this problem with one line of code why did I walk you through this long painful example of using the Activity’s life cycle methods to preserve the text?  The reason is so I could fill you with knowledge about life, well knowledge about life cycle that is.  Anyone who is aspiring to become an Android developer needs to understand an Activity’s life cycle like the back of their hand, and there is no better way of engraining this into your mind then by making you suffer through a long tedious solution to a simple problem.&lt;/p&gt;

&lt;p&gt;Now that you have been painfully introduced to an Activity and it life cycle let’s go-ahead flip the script a little bit and discuss iOS View Controllers.&lt;/p&gt;

&lt;h4 id=&quot;view-controllers&quot;&gt;View Controllers:&lt;/h4&gt;

&lt;p&gt;A &lt;a href=&quot;https://developer.apple.com/library/ios/featuredarticles/ViewControllerPGforiPhoneOS/index.html-//apple_ref/doc/uid/TP40007457-CH2-SW1&quot;&gt;View Controller&lt;/a&gt; and an Activity are similar in many ways but have a few key differences. Similar to an Activity, a View Controller is the controller in the MVC architecture. View Controllers are also similar to Activities in the sense that every application must have at least one View Controller and pretty much every application has more than one. The general rule with iOS applications is that every separate screen that is presented to a user should have its own View Controller.  The reason for this is because Apple strongly suggests that all applications developed for iOS should follow the MVC architecture. Typically a View Controller manages one view (and all of it’s subviews) associated with it that it uses to display and receive information from the user. Similar to Activities, View Controllers also have a life cycle. However, it does differ slightly from that of an Activity. A View Controller has the following life cycle methods, &lt;code&gt;loadView()&lt;/code&gt;, &lt;code&gt;viewDidLoad()&lt;/code&gt;, &lt;code&gt;viewWillAppear()&lt;/code&gt;, &lt;code&gt;viewDidAppear()&lt;/code&gt;, &lt;code&gt;viewWillDisappear()&lt;/code&gt;, and &lt;code&gt;viewDidDisappear()&lt;/code&gt;.  So now that you have had a little background on what a View Controller is, let’s jump into another example doing the same thing we did earlier with our Activity example.&lt;/p&gt;

&lt;p&gt;First let’s start by creating a new Single View Application project in Xcode and selecting Swift as the language. You can set the product name as whatever you like, but for my example I am going to use the name ViewControllerExample. Now that we have a new project up and running let’s get rid of all of the storyboard files. For now, we will define our layout programmatically to better understand how the ViewController works. Go ahead and delete the &lt;code&gt;Main.storyboard&lt;/code&gt; and the &lt;code&gt;LaunchScreen.storyboard&lt;/code&gt; files. Make sure that you select the “remove reference” option for both of these files. After that open up &lt;code&gt;Info.plist&lt;/code&gt; and delete the key-value pairs for both the “Launch screen interface file base name” and the “Main storyboard file base name”.  Go ahead and run the project. You should see a black screen. If your program crashed go back and make sure that you deleted all of the correct files and key-values from the &lt;code&gt;Info.plist&lt;/code&gt;. Now that we have set up our project it’s time to add a text box to the center of our screen. But before we add a text box to our screen we need to set up our window in the App Delegate. The App Delegate is similar to a Main Activity in Android because it is essentially the control center for the application, it is responsible for setting up the application on launch and taking care of application clean up when it enters the background or is destroyed.  Navigate to &lt;code&gt;AppDelegate.swift&lt;/code&gt; and add the following code to &lt;code&gt;application(application:didFinishLaunchingWithOptions:)&lt;/code&gt;&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-swift&quot; data-lang=&quot;swift&quot;&gt;&lt;span class=&quot;kd&quot;&gt;func&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;application&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;application&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;UIApplication&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;didFinishLaunchingWithOptions&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;launchOptions&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;NSObject&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;AnyObject&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]?)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Bool&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;//Make the view Controller&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;let&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;viewController&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;UIViewController&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;ViewController&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;viewController&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;view&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;backgroundColor&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;UIColor&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;blackColor&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()&lt;/span&gt;

        &lt;span class=&quot;c1&quot;&gt;//Set up the window&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;window&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;UIWindow&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;window&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;?&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;rootViewController&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;viewController&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;window&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;?&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;makeKeyAndVisible&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()&lt;/span&gt;

        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;true&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Now run your application again. You should still see a black screen. But don’t worry we are getting close to having our text box up and running. Now navigate to &lt;code&gt;ViewContoller.swift&lt;/code&gt; and modify &lt;code&gt;viewDidLoad()&lt;/code&gt; like so,&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-swift&quot; data-lang=&quot;swift&quot;&gt;&lt;span class=&quot;k&quot;&gt;override&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;func&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;viewDidLoad&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;viewDidLoad&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()&lt;/span&gt;

        &lt;span class=&quot;k&quot;&gt;let&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;textField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;UITextField&lt;/span&gt;  &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;UITextField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;textField&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;frame&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CGRectMake&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;view&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;bounds&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;/&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;100&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;),&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;view&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;bounds&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;/&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;20&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;),&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;200&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;40&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;textField&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;backgroundColor&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;UIColor&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;whiteColor&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;view&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;addSubview&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;textField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;

&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Now note that we could have put this same code in &lt;code&gt;viewWillAppear()&lt;/code&gt; or &lt;code&gt;viewDidAppear()&lt;/code&gt; and it would have worked just fine for this simple example. The only difference is that &lt;code&gt;viewDidLoad()&lt;/code&gt; is called once after the view controller’s view has been created, and the appear methods are called every time the view controller becomes visible. If we were to add the view in either appear method, a new view would be added every time the view controller became visible (after navigating back from a subsequent screen, for example), which is not what we want because it is extremely inefficient. However, once again keep in mind that even using &lt;code&gt;viewDidLoad()&lt;/code&gt; is not the proper way of setting up a view for an iOS application. In a real application you should create your own custom view and add a UITextField to that view and then use &lt;code&gt;loadView()&lt;/code&gt; in the ViewController class to load in your custom view. But for this example we will again stick with the quick and dirty way of doing things.&lt;/p&gt;

&lt;p&gt;Run your project again. You should now see a white text box in the center of the screen. Now that we finally have a text box up on screen let’s test it out. Let’s do the same thing that we did earlier with our ActivityExample. Let’s enter some text into the text box and change the device orientation (If you are working on a Mac you can rotate the screen by using holding down the command key and pressing either the right or left arrow keys). But before you actually test this out, what you do you expect to happen? Do you think your text will be deleted like in the Activity Example from earlier? Or do you think it will stick around this time?  Go ahead and run it so you can find out.&lt;/p&gt;

&lt;p&gt;Surprise, the text stuck around like leader of the Brotherhood Without Banners after losing his battle with the Hound. So what caused the text to stick around, the Lord of Light? Well not exactly. Android destroys the Activity to allow you to handle changes in configuration (device orientation, device language) and allows you to load a different layout. In iOS on the other hand, you will need to handle those device configuration changes yourself. If you think about it, it’s extremely inefficient to completely destroy and recreate a View Controller every time that a device is rotated. Of course this implementation does still have its downsides. As you will notice the text box is no longer centered in the screen. The reason for this is because it only lays itself out based on its original portrait screen dimensions when it was first drawn.  Orientation changes don’t automatically trigger another layout pass.  So how can we fix this? Do we need to override &lt;code&gt;viewWillDisappear()&lt;/code&gt; or &lt;code&gt;viewDidDisappear()&lt;/code&gt; similar to what we did in the Activity example above? Unfortunately this will not work because the View Controller never disappears during rotation. In fact these methods are only called when a View Controller’s view disappears from the screen. They do not even get called when the application is destroyed. Instead Apple chose to have a single control center take care the clean up that should happen when an application is destroyed, and that control center is AppDelegate.  So any calls to file saving methods should be called in the AppDelegate method &lt;code&gt;applicationWillTerminate()&lt;/code&gt; rather than in a specific View Controller. So how can we reposition our text box if none of the View Controller’s life cycle methods are called during rotation? Well believe it or not Apple realized this problem and provided us with the method &lt;code&gt;viewWillLayoutSubviews()&lt;/code&gt;. To fix this issue elevate textField to an instance variable and add the following code to ViewController.swift&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-swift&quot; data-lang=&quot;swift&quot;&gt;&lt;span class=&quot;k&quot;&gt;override&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;func&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;viewWillLayoutSubviews&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;textField&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;frame&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CGRectMake&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;view&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;bounds&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;/&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;100&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;),&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;view&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;bounds&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;/&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;20&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;),&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;200&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;40&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;There, now we have a text box with the correct text located in the center of the screen. But the one thing that I’m sure some of you realized is that we are redrawing the text box on the screen. So won’t this perform just as poorly as the Android implementation of &lt;code&gt;onDestroy()&lt;/code&gt;? The answer is sort of. It does have to redraw the view, but it doesn’t have to actually kill the View Controller and re create it like we did in the Activity example above. So for that reason it performs better than the Activity implementation that Google chose.&lt;/p&gt;

&lt;h4 id=&quot;summary&quot;&gt;Summary&lt;/h4&gt;

&lt;p&gt;Both examples have their drawbacks and you can see the pros and cons of developing this simple application on both platforms.  I’m sure that by now you can start to see how the iOS vs Android battle can become a heated debate pretty quickly because they do similar things but in different fashions. During the remainder of this series I will cover a number of other differences between the two platforms and help you make an informed decision on which platform you think is better. So don’t worry, if you haven’t already picked a side in the Android vs. iOS battle there is still plenty of time left. After all, the Battle of the bOStards is just beginning.&lt;/p&gt;

&lt;p&gt;Also keep in mind that there are a number of other differences between Activities and View Controllers, but for the sake of your time and mine I choose to keep this article fairly short and straightforward. If you want to learn more about the differences between the two, check out the official documentation provided by Google and Apple by using the following links.&lt;/p&gt;

&lt;ul&gt;
&lt;li&gt;Activities: &lt;a href=&quot;https://developer.android.com/guide/components/activities.html&quot;&gt;https://developer.android.com/guide/components/activities.html&lt;/a&gt;&lt;/li&gt;
&lt;li&gt;View Controllers: &lt;a href=&quot;https://developer.apple.com/library/ios/featuredarticles/ViewControllerPGforiPhoneOS/index.html-//apple_ref/doc/uid/TP40007457-CH2-SW1&quot;&gt;https://developer.apple.com/library/ios/featuredarticles/ViewControllerPGforiPhoneOS/index.html-//apple_ref/doc/uid/TP40007457-CH2-SW1&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
</description>
        <pubDate>Fri, 12 Aug 2016 00:00:00 -0600</pubDate>
        <link>http://www.pixio.com/blog/2016-08-12/activities-vs-view-controllers/</link>
        <guid isPermaLink="true">http://www.pixio.com/blog/2016-08-12/activities-vs-view-controllers/</guid>
        
        <category>android</category>
        
        <category>ios</category>
        
        
        <category>programming</category>
        
      </item>
    
      <item>
        <title>A Nibble of Gradle Flavors</title>
        <description>&lt;p&gt;In Android Studio, &lt;a href=&quot;https://developer.android.com/studio/build/index.html&quot;&gt;Gradle&lt;/a&gt; is used as a build tool with the &lt;a href=&quot;https://developer.android.com/studio/releases/gradle-plugin.html&quot;&gt;Android plugin&lt;/a&gt; to configure your project and create an APK. Though most developers use Gradle to build their project, many of them don&amp;#39;t take full advantage of Gradle scripts. One of the most common use cases is creating different &lt;a href=&quot;http://google.github.io/android-gradle-dsl/current/com.android.build.gradle.internal.dsl.ProductFlavor.html&quot;&gt;product flavors&lt;/a&gt; for their app. Flavors essentially let you build different versions of your app using a single code base.&lt;/p&gt;

&lt;p&gt;While there are a lot of very simple apps that don&amp;#39;t really need different flavors, many developers use the &lt;strong&gt;Demo&lt;/strong&gt;/&lt;strong&gt;Paid&lt;/strong&gt; paradigm to monetize their applications. Another common useful case is when you have a production server and a staging server, flavors can you help you make apps to use the corresponding server. There&amp;#39;s many reasons why a flavor would be nice or necessary, let&amp;#39;s dive in a little deeper at how easy it is to accomplish this.&lt;/p&gt;

&lt;h3 id=&quot;which-flavor-is-right-for-you&quot;&gt;Which Flavor is right for you?&lt;/h3&gt;

&lt;p&gt;To start off, open the &lt;code&gt;build.gradle&lt;/code&gt; for the &lt;em&gt;module&lt;/em&gt; of your Android project (not the &lt;code&gt;build.gradle&lt;/code&gt; for the &lt;em&gt;project&lt;/em&gt;). It should look similar to:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-groovy&quot; data-lang=&quot;groovy&quot;&gt;&lt;span class=&quot;n&quot;&gt;apply&lt;/span&gt; &lt;span class=&quot;nl&quot;&gt;plugin:&lt;/span&gt; &lt;span class=&quot;s1&quot;&gt;'com.android.application'&lt;/span&gt;

&lt;span class=&quot;n&quot;&gt;android&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;...&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;defaultConfig&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;applicationId&lt;/span&gt; &lt;span class=&quot;s2&quot;&gt;&quot;com.pixio.awesomeapp&quot;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;...&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;versionCode&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;versionName&lt;/span&gt; &lt;span class=&quot;s2&quot;&gt;&quot;1.0&quot;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;buildTypes&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;...&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;o&quot;&gt;...&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;By adding just a few lines, we can have different flavors.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-groovy&quot; data-lang=&quot;groovy&quot;&gt;&lt;span class=&quot;n&quot;&gt;android&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;...&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;productFlavors&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;free&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;applicationId&lt;/span&gt; &lt;span class=&quot;s1&quot;&gt;'com.pixio.awesomeapp.free'&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;resValue&lt;/span&gt; &lt;span class=&quot;s2&quot;&gt;&quot;string&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s2&quot;&gt;&quot;app_name&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s2&quot;&gt;&quot;Awesome App (FREE)&quot;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;paid&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;applicationId&lt;/span&gt; &lt;span class=&quot;s1&quot;&gt;'com.pixio.awesomeapp.paid'&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;resValue&lt;/span&gt; &lt;span class=&quot;s2&quot;&gt;&quot;string&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s2&quot;&gt;&quot;app_name&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s2&quot;&gt;&quot;Awesome app+&quot;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Simple and easy. As shown above, I have overwritten the name of the app and the application id depending on which flavor is built (&lt;code&gt;app_name&lt;/code&gt; is the default field to store the name of the app displayed to the user). Anything that is defined in &lt;code&gt;defaultConfig&lt;/code&gt; can be overridden by any/all flavors to further customize the different apps. To actually make use of these newly defined flavors, we need to &lt;strong&gt;sync our project with gradle files&lt;/strong&gt; (&lt;em&gt;Tools&lt;/em&gt; -&amp;gt; &lt;em&gt;Android&lt;/em&gt; -&amp;gt; &lt;em&gt;Sync project with gradle files&lt;/em&gt;).&lt;/p&gt;

&lt;p&gt;Well now we have our flavors declared, how do we build them? In Android Studio, open the &lt;strong&gt;Build Variants&lt;/strong&gt; window (&lt;em&gt;View&lt;/em&gt; -&amp;gt; &lt;em&gt;Tool Windows&lt;/em&gt; -&amp;gt; &lt;em&gt;Build Variants&lt;/em&gt;). If you have synced with gradle, you should now see a window that shows which module you are working with and which &lt;a href=&quot;https://developer.android.com/studio/build/build-variants.html&quot;&gt;Build Variant&lt;/a&gt; you&amp;#39;re working with. If you click on the &lt;em&gt;Build Variant&lt;/em&gt; box, a dropdown will appear letting you pick the &lt;code&gt;Debug&lt;/code&gt; and &lt;code&gt;Release&lt;/code&gt; build types of your defined flavors. These build types can each be combined with each flavor to determine which keystore will be used when signing your apk during the build process. Generally, you&amp;#39;ll want to work with the &lt;code&gt;Debug&lt;/code&gt; variant when developing and the &lt;code&gt;Release&lt;/code&gt; variant when building an APK for beta testing and the Play Store.&lt;/p&gt;

&lt;h3 id=&quot;build-config&quot;&gt;Build Config&lt;/h3&gt;

&lt;p&gt;With the different flavors now set up, we can customize the app&amp;#39;s behavior even further by adding new [build config fields][build-config]. These fields are added in the same &lt;code&gt;build.gradle&lt;/code&gt; that we&amp;#39;ve been working in, and can be added to flavors as well as build types. We can define unique values by adding lines like the following to any flavor:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-groovy&quot; data-lang=&quot;groovy&quot;&gt;&lt;span class=&quot;n&quot;&gt;buildConfigField&lt;/span&gt; &lt;span class=&quot;s1&quot;&gt;'String'&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s1&quot;&gt;'HOST'&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s1&quot;&gt;'&quot;staging.pixioserver.com&quot;'&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;With that specific example, we defined &lt;code&gt;BuildConfig.HOST&lt;/code&gt; to have the value &lt;code&gt;&amp;quot;staging.pixioserver.com&lt;/code&gt;. This allows us to have a specific endpoint for our staging flavor app that is different from the release version, which points to some production endpoint. Then, by building our app in the corresponding &lt;code&gt;Staging&lt;/code&gt; and &lt;code&gt;Production&lt;/code&gt; versions, we get the server intended for that app.&lt;/p&gt;

&lt;p&gt;We can add any valid java type as a &lt;code&gt;buildConfigField&lt;/code&gt; with any valid java variable name. This could be useful for defining specific flavors/variants that need to report bug crashes or to not allow certain features using boolean flags. For example, you can enable a feature that let’s you view server logs or debug data in certain debugging/client versions of the app.&lt;/p&gt;

&lt;h3 id=&quot;that-39-s-a-gradle-wrap&quot;&gt;That&amp;#39;s A (Gradle) Wrap!&lt;/h3&gt;

&lt;p&gt;This was just a small touch of the power you can use when customizing your &lt;code&gt;build.gradle&lt;/code&gt;. A sample of things you can do are set your project up to automatically sign the apk with a specified keystore, defining custom build procedures when compiling the project, or even modifying the apk after building to include the version number. Using these concepts we can define custom flavors to achieve multiple Android apps using the &lt;em&gt;same&lt;/em&gt; codebase. By using flavors, we can specify special &lt;code&gt;buildConfigField&lt;/code&gt; properties that further define the behavior of each app and let developers have more control over testing/paid/branded versions. With a little more work, you can actually have code separated into different &lt;a href=&quot;https://developer.android.com/studio/build/build-variants.html#sourcesets&quot;&gt;source sets&lt;/a&gt; that allow you to control the flow of your app with finer control by executing code blocks for corresponding flavors.&lt;/p&gt;

&lt;p&gt;[build-config]: &lt;http://google.github.io/android-gradle-dsl/current/com.android.build.gradle.internal.dsl.ProductFlavor.html#com.android.build.gradle.internal.dsl.ProductFlavor:buildConfigField(java.lang.String, java.lang.String, java.lang.String)&gt;&lt;/p&gt;
</description>
        <pubDate>Fri, 05 Aug 2016 00:00:00 -0600</pubDate>
        <link>http://www.pixio.com/blog/2016-08-05/a-nibble-of-gradle-flavors/</link>
        <guid isPermaLink="true">http://www.pixio.com/blog/2016-08-05/a-nibble-of-gradle-flavors/</guid>
        
        <category>android</category>
        
        <category>gradle</category>
        
        
        <category>programming</category>
        
      </item>
    
      <item>
        <title>Wrap Battle: Wrapping C with Swift and Java</title>
        <description>&lt;p&gt;There are many situations in which a shared codebase is desirable. Perhaps your project involves a lot of calculations which you want to be carried out by the exact same code on all your platforms to ensure that the results are identical. Maybe you inherited a large C/C++ codebase or rely on a library that needs to work in your iOS or Android apps and rewriting it is not an option. You might simply prefer to write the bulk of your code in a shared language so that you aren&amp;#39;t testing and validating the same functions in two or more languages.&lt;/p&gt;

&lt;p&gt;In this article I present two approaches to wrapping the functionality of a C interface in Swift and Java, highlighting what does and does not work well for each language. The techniques presented below are not the only ways to accomplish what I set out to do, but they are the most common wrapping styles I have encountered, which is why I chose them over other approaches. The code I present here is also relatively free of &amp;quot;magic tricks&amp;quot; that optimize the code&amp;#39;s efficiency at the expense of immediate readability, so don&amp;#39;t go and use this code as the basis for your next high-performance math library without refining it a bit.&lt;/p&gt;

&lt;p&gt;We have written a lot lately about the design of &lt;a href=&quot;http://pixio.com/blog/2016-06-03/c-in-the-21st-century/&quot; title=&quot;C in the 21st Century&quot;&gt;shared object systems&lt;/a&gt; and &lt;a href=&quot;http://pixio.com/blog/2016-07-08/how-to-score-big-with-androids-ndk/&quot; title=&quot;How to Score Big with Android&amp;#39;s NDK&quot;&gt;JNI integration for C on Android&lt;/a&gt;, so I won&amp;#39;t re-tread that ground here. If you are curious about how to set up a project in either Android Studio or Xcode to do what I describe in this article, look at those earlier articles and/or feel free to check out the &lt;a href=&quot;https://github.com/Dave-Heyborne/WrapBattle&quot; title=&quot;WrapBattle GitHub Repository&quot;&gt;the example repository&lt;/a&gt; for this article. Also, note that the code presented below is a subset of the code in the example repository - many code sections were left out of the article for clarity&amp;#39;s sake.&lt;/p&gt;

&lt;h2 id=&quot;c-library&quot;&gt;C Library&lt;/h2&gt;

&lt;p&gt;To get started, I will cover the C library I plan to wrap. First is the &amp;#39;data object&amp;#39; in question - a 3D vector represented as a struct:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;k&quot;&gt;typedef&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;This is a very simple struct to use, either by directly instantiating it on the stack or by using a convenience constructor that returns a pointer to a heap-allocated struct:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Stack Construction
&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;vector&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;};&lt;/span&gt;

&lt;span class=&quot;c1&quot;&gt;// Pointer Constructor
&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;__attribute__&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;malloc&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;nothrow&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;returns_nonnull&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;warn_unused_result&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;))&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3DCreate_P&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;vector&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;malloc&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;sizeof&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;));&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;vector&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;vector&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;vector&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;vector&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;c1&quot;&gt;// Pointer Construction
&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;vectorPointer&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3DCreate_P&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Once an instance of the struct has been obtained, it can be manipulated with some simple functions (for example, the cross product function):&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Pass-By-Value Cross Product
&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;__attribute__&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;nothrow&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;warn_unused_result&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;))&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3DCrossProduct&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;){(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;),&lt;/span&gt;
                             &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;),&lt;/span&gt;
                             &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)};&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;c1&quot;&gt;// Pass-By-Pointer Cross product
&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;__attribute__&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;malloc&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;nonnull&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;nothrow&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;returns_nonnull&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;warn_unused_result&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;))&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3DCrossProduct_P&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;crossProduct&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;malloc&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;sizeof&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;));&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;crossProduct&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;crossProduct&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;crossProduct&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;left&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;right&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;crossProduct&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;All of this should be fairly straightforward. But how can this code be effectively wrapped by Swift and Java for use in mobile applications? Two common approaches to doing this are either making wrapper classes that internally hold a reference to a C struct, or trying to replicate the struct directly in the target language (generally performing a conversion to pass the struct into C functions that expect value parameters). As will be shown below, these techniques differ greatly in how useful and simple they are between Swift and Java.&lt;/p&gt;

&lt;h2 id=&quot;swift-wrappers&quot;&gt;Swift Wrappers&lt;/h2&gt;

&lt;p&gt;To start, here are the Swift implementations of each wrapper paradigm, starting with the value wrapper:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-swift&quot; data-lang=&quot;swift&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Value 'Wrapper'&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;extension&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CVector3D&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;    
    &lt;span class=&quot;k&quot;&gt;mutating&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;func&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;self&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CVector3DAdd&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;self&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;func&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;crossProduct&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CVector3D&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CVector3DCrossProduct&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;self&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Notice that this is, in fact, not a wrapper class at all, but rather an extension on the C struct directly. Because C is (mostly) seamlessly bridged into Swift, it is possible to use non-opaque C structs directly in Swift code as though they were regular Swift structs.&lt;/p&gt;

&lt;p&gt;That being said, many libraries manipulate struct instances &amp;quot;by reference&amp;quot; via pointers to heap-allocated memory, rather than by modifying and passing around structs by value. Oftentimes these pointers are also opaque and the struct definition is not visible from the library&amp;#39;s interface, so even if you wanted to use the structs by value in Swift, you couldn&amp;#39;t. Below is the implementation of a Swift class that wraps a pointer to a C vector:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-swift&quot; data-lang=&quot;swift&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Pointer Wrapper&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Vector3D&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;var&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;UnsafeMutablePointer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt;

    &lt;span class=&quot;nf&quot;&gt;init&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CDouble&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CDouble&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CDouble&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CVector3DCreate_P&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;init&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;UnsafeMutablePointer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;self&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;deinit&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kt&quot;&gt;CVector3DDestroy_P&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;var&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CDouble&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;get&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pointee&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;set&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pointee&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newValue&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;var&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CDouble&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;get&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pointee&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;set&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pointee&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newValue&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;var&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CDouble&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;get&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pointee&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;set&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pointee&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;newValue&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;func&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Vector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kt&quot;&gt;CVector3DAdd_P&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;func&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;crossProduct&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Vector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Vector3D&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Vector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CVector3DCrossProduct_P&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;))&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Notice the extra infrastructure above that deals with keeping a reference to a pointer, and the &lt;code&gt;deinit&lt;/code&gt; function which ensures that the memory associated with the pointer is freed once the Swift object is deallocated. A private init function is also needed to create new &lt;code&gt;Vector3D&lt;/code&gt; wrappers for the return values of C functions that return pointers to new &lt;code&gt;CVector3D&lt;/code&gt;s. The struct extension didn&amp;#39;t have to account for manual memory management (because the by-value struct functions don&amp;#39;t allocate heap memory) or wrapping return values, so the wrapper class feels distinctly inferior.&lt;/p&gt;

&lt;p&gt;Below are some examples of using each of the above vector implementations:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-swift&quot; data-lang=&quot;swift&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Value 'Wrapper' Usage&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;var&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;cVector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CVector3D&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;1.0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;1.0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;1.0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;cVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;1.0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;1.0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;1.0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;))&lt;/span&gt;

&lt;span class=&quot;c1&quot;&gt;// Pointer Wrapper Usage&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;let&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;vector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Vector3D&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Vector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;1.0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;1.0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;1.0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;vector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Vector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;1.0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;1.0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;1.0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;))&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;As you can see, both wrapper methods are quite simple and using the resulting implementations feels similar. However, the struct extension is (in my opinion) the clear winner of the two strategies for Swift if the programmer has access to the struct definition. It does not introduce a new type, directly uses the existing C functions with no modification, and doesn&amp;#39;t necessitate any kind of memory management or boxing/unboxing on the part of the implementer.&lt;/p&gt;

&lt;h2 id=&quot;java-wrappers&quot;&gt;Java Wrappers&lt;/h2&gt;

&lt;p&gt;Moving on to the Java side, here is the Java implementation of a value wrapper for the &lt;code&gt;CVector3D&lt;/code&gt; struct, which tries to get as close as Java allows to having a &amp;quot;struct&amp;quot; (but due to the fact that it is actually a class, it won&amp;#39;t actually work as a struct in Java the way that it does in Swift).&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// 'Value' Wrapper&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;Vector3DStruct&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;Vector3DStruct&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;z&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getX&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;setX&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getY&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;setY&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getZ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;setZ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;z&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Vector3DStruct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3DStruct&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;crossProduct&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Vector3DStruct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Since Java does not natively support C structs, the struct is almost entirely rewritten to support interacting with it as a Java object. Unlike a &amp;quot;real&amp;quot; struct, this Java object will not be treated as a value type, meaning that if one is modified within a function the changes will persist outside the function. The class methods marked with the &lt;code&gt;native&lt;/code&gt; keyword are implemented on the C side via the JNI, as shown below:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;n&quot;&gt;JNIEXPORT&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;JNICALL&lt;/span&gt;
&lt;span class=&quot;nf&quot;&gt;Java_com_pixio_dave_Vectors_Vector3DStruct_add&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;JNIEnv&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jclass&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetObjectClass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;xID1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;x&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;D&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;yID1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;y&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;D&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;zID1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;z&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;D&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;xID1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;yID1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;zID1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jclass&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetObjectClass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;xID2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;x&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;D&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;yID2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;y&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;D&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;zID2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;z&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;D&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;xID2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;yID2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;zID2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3DAdd&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;){&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;},&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;){&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;});&lt;/span&gt;

    &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;SetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;xID1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;SetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;yID1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;SetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;zID1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;n&quot;&gt;JJNIEXPORT&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;JNICALL&lt;/span&gt;
&lt;span class=&quot;nf&quot;&gt;Java_com_pixio_dave_Vectors_Vector3DStruct_crossProduct&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;JNIEnv&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jclass&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetObjectClass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;xID1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;x&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;D&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;yID1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;y&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;D&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;zID1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;z&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;D&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;xID1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;yID1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;zID1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jclass&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetObjectClass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;xID2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;x&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;D&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;yID2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;y&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;D&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;zID2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;z&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;D&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;xID2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;yID2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetDoubleField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;zID2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3DCrossProduct&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;){&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;},&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;){&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;});&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jmethodID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;constructor&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetMethodID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;&amp;lt;init&amp;gt;&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;(DDD)V&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;NewObject&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;constructor&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Constructing three new vectors just to add one vector to another is, to put it mildly, not great. While some of the class lookup code could be optimized here, the primary problem is that every time a C pass-by-value function needs to be called on the Java object &amp;quot;struct&amp;quot;&amp;#39;, an actual C struct has to be built from that Java object. While the &lt;code&gt;CVector3D&lt;/code&gt; struct may not be complex enough to make this operation prohibitively expensive, a more complicated struct would quickly rule out using the above sort of wrapper due to the incredibly wasteful process of round-tripping a Java object into a C struct and then back into a Java object again. It would be far more efficient to simply rewrite the class in pure Java or rewrite the C functions in the JNI layer rather than do all the boxing and unboxing of C structs shown here.&lt;/p&gt;

&lt;p&gt;Here is the way that the pointer/reference wrapper class is implemented in Java:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Pointer Wrapper&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;Vector3DPointer&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;long&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;Vector3DPointer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;reference&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3DPointer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;createReference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;Vector3DPointer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;long&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;reference&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;protected&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;finalize&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;throws&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Throwable&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;Vector3DPointer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;destroyReference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;finalize&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getX&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;setX&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getY&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;setY&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getZ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;setZ&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Vector3DPointer&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3DPointer&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;crossProduct&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Vector3DPointer&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;long&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;createReference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;double&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;destroyReference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;long&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;This wrapper class looks quite similar to the Swift pointer wrapper class, and behaves similarly. A pointer is stored internally as a &lt;code&gt;long&lt;/code&gt;, and the Java object&amp;#39;s &lt;code&gt;finalize()&lt;/code&gt; method ensures that the memory associated with the pointer is freed when the Java object is about to be deallocated. Here are some of the JNI functions that back the native calls in the class above:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;n&quot;&gt;JNIEXPORT&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;JNICALL&lt;/span&gt;
&lt;span class=&quot;nf&quot;&gt;Java_com_pixio_dave_Vectors_Vector3DPointer_setX&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;JNIEnv&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jdouble&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jclass&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetObjectClass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;referenceID&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;reference&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;J&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)((&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetLongField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;referenceID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;));&lt;/span&gt;

    &lt;span class=&quot;n&quot;&gt;reference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;n&quot;&gt;JNIEXPORT&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;JNICALL&lt;/span&gt;
&lt;span class=&quot;nf&quot;&gt;Java_com_pixio_dave_Vectors_Vector3DPointer_add&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;JNIEnv&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jclass&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetObjectClass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;referenceID1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;reference&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;J&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)((&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetLongField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;referenceID1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;));&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jclass&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetObjectClass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;referenceID2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;reference&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;J&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)((&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetLongField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;referenceID2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;));&lt;/span&gt;

    &lt;span class=&quot;n&quot;&gt;CVector3DAdd_P&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;reference1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;n&quot;&gt;JNIEXPORT&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;JNICALL&lt;/span&gt;
&lt;span class=&quot;nf&quot;&gt;Java_com_pixio_dave_Vectors_Vector3DPointer_crossProduct&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;JNIEnv&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jclass&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetObjectClass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;referenceID1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;reference&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;J&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference1&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)((&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetLongField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;referenceID1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;));&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jclass&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetObjectClass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;referenceID2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;reference&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;J&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)((&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetLongField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;other&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;referenceID2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;));&lt;/span&gt;

    &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3DCrossProduct_P&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;reference1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jmethodID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;constructor&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetMethodID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;&amp;lt;init&amp;gt;&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;(J)V&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;NewObject&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Vector3D1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;constructor&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;jlong&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;result&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The JNI pass-by-pointer methods essentially just have to obtain the pointers from the Java object and then call the C pass-by-pointer functions to carry out their work. Because the Java object here only holds a pointer to the struct rather than the data of the struct itself, changes to the struct can be carried out much more easily and without making the redundant copies seen in the pass-by-value approach. To more directly compare the pass-by-value and pass-by-pointer approaches for Java, look at the following excerpts from the JNI methods below:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Critical Section of Pass-By-Value JNI Method&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3DCrossProduct&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;kd&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;){&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;},&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kd&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;){&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;x2&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y2&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;z2&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;});&lt;/span&gt;

&lt;span class=&quot;c1&quot;&gt;// Critical Section of Pass-By-Pointer JNI Method&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;CVector3D&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;result&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CVector3DCrossProduct_P&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;reference1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;reference2&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Again, notice that the pass-by-value function is rebuilding C structs to pass them into the C function, while the pass-by-pointer function only passes in pointer values. While in this example a 3-element struct might not be far worse than a pointer in terms of overhead, it should be easy to imagine how awful the pass-by-value approach could become as the number and complexity of items in the struct increased. No matter how complicated the struct became, the pass-by-pointer approach is only going to pass a single pointer.&lt;/p&gt;

&lt;h2 id=&quot;conclusions&quot;&gt;Conclusions&lt;/h2&gt;

&lt;p&gt;As I mentioned before, the examples above are not the only way of wrapping C structs and their functionality in Swift or Java. However, even these two examples clearly show that the optimal process is significantly different between those two languages. Even if the above code were carefully optimized, my preference for how to wrap C on the Swift side would differ from my preference on the Java side. Swift&amp;#39;s support for C structs natively makes it almost a no-brainer to use the structs by value and add capabilities via extensions (unless pass-by-reference behavior is desired on the Swift side). In fact, Apple has been doing exactly this to enhance their C APIs for use with Swift. Java&amp;#39;s lack of such support means that wrapping a pointer in a Java class ends up being much cleaner, as it does not require a lot of reimplementation of object structure on the Java side.&lt;/p&gt;

&lt;p&gt;While wrapping C on either Swift or Java is relatively straightforward, wrapping the same C code in Swift AND Java simultaneously takes a lot more effort. The pointer wrapper approach is generally the superior option of the two I have presented if both Swift and Java require support, because the value wrapper approach can quickly become prohibitively inefficient on the Java side. An even better option, assuming that total control of the C codebase is possible, is to engineer the C library in such a way that Swift and Java tie-ins are part of the design from the start. The C code in this article was deliberately designed to implement two different versions of the same functionality - in reality, one of those sets of functions (pass-by-value or pass-by-pointer) could have been reworked to depend on the other to reduce duplication, and the way the data was being manipulated could have been designed in a more Java-friendly way. These sorts of optimizations are best suited to a future article, but are important to mention, and to consider if you decide to start implementing a shared library.&lt;/p&gt;
</description>
        <pubDate>Fri, 22 Jul 2016 00:00:00 -0600</pubDate>
        <link>http://www.pixio.com/blog/2016-07-22/wrap-battle-wrapping-c-with-swift-and-java/</link>
        <guid isPermaLink="true">http://www.pixio.com/blog/2016-07-22/wrap-battle-wrapping-c-with-swift-and-java/</guid>
        
        <category>c</category>
        
        <category>swift</category>
        
        <category>java</category>
        
        <category>JNI</category>
        
        <category>FFI</category>
        
        
        <category>programming</category>
        
      </item>
    
      <item>
        <title>C Considered Awesome</title>
        <description>&lt;p&gt;&lt;sup&gt;&lt;sup&gt;Everything written here is garbage and you should not listen to a word of it.  Enjoy.&lt;/sup&gt;&lt;/sup&gt;&lt;/p&gt;

&lt;p&gt;With so many languages, platforms, and frameworks in today&amp;#39;s modern computer development world, it&amp;#39;s easy to lose sight of the foundations of the field that have made computing great.  Without question one of those pillars is the C programming language.  C is &lt;em&gt;everywhere&lt;/em&gt;, it&amp;#39;s all around us, even now in this very room.  You can see it when you look out your window (probably), or when you turn on your television (almost definitely).  You use it when you go to work, when you go to church, when you pay your taxes. C underlies much of the computing done today whether you know it or not. And that&amp;#39;s what makes it so important.&lt;/p&gt;

&lt;p&gt;But beyond importance, it&amp;#39;s a great language to work with.  There are so many subtle features and tricks you can take advantage of that have been folded into the intricate, time-tested fabric of the C language (and its derivative languages).  It&amp;#39;s cool that you can write a website with 4 characters of ruby code or make make the next $1Trillion app by drag and dropping a zipped text file into a web service, but some engineering challenges really do &lt;em&gt;need&lt;/em&gt; to be solved.  And sometimes those problems are best solved with low-level, performant, close-to-the-metal, no-holds-barred, potentially-cryptic, always-awesome C code.&lt;/p&gt;

&lt;p&gt;But let&amp;#39;s talk about why you&amp;#39;re here.  You&amp;#39;re here to learn some of those tricks that make C the greatest language around.  I will warn you that if you use some of these in your own projects, your less-enlightened coworkers may begin to fear or despise your clear mastery of the art of the code.  But soldier on.  These tricks will almost definitely make your code the most memorable and unique works of typography at your firm. You may even begin to receive attention from upper management that could potentially have life-changing effects on your career.&lt;/p&gt;

&lt;p&gt;Are you ready?&lt;/p&gt;

&lt;h2 id=&quot;c-tricks-your-instructor-never-told-you-about&quot;&gt;C Tricks Your Instructor Never Told You About&lt;/h2&gt;

&lt;p&gt;Think of these tricks as lifehacks for code.  Once you know about them, you won&amp;#39;t be able to help but sprinkle them around your code.  And the impact of this will be hard to miss.&lt;/p&gt;

&lt;h3 id=&quot;c-supports-inline-citations-right-in-your-code&quot;&gt;C supports inline citations right in your code&lt;/h3&gt;

&lt;p&gt;Have you ever been stumped?  Don&amp;#39;t worry, it happens to everyone.  But sometimes other people were stumped before you by the same problem. When they solved it, they posted their solutions for all to see. But you probably don&amp;#39;t want to steal their implementation outright.  If your boss found out, they might think you don&amp;#39;t know how to do your job.&lt;/p&gt;

&lt;p&gt;Let&amp;#39;s turn the tables.  After seeing this advanced knowledge in action, your boss will have no question of your skill and you get to use the code you found without fear.&lt;/p&gt;

&lt;p&gt;Let&amp;#39;s see it in action.  Your boss asks you to fill out this method:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;print_sevenTimes&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;char&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;size_t&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;len&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// Do your job here
&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;So you come up with a solution:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;print_sevenTimes&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;char&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;size_t&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;len&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// ensure null termination
&lt;/span&gt;    &lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;len&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;

    &lt;span class=&quot;n&quot;&gt;printf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;%s&lt;/span&gt;&lt;span class=&quot;se&quot;&gt;\n&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// 1
&lt;/span&gt;    &lt;span class=&quot;n&quot;&gt;printf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;%s&lt;/span&gt;&lt;span class=&quot;se&quot;&gt;\n&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// 2
&lt;/span&gt;    &lt;span class=&quot;n&quot;&gt;printf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;%s&lt;/span&gt;&lt;span class=&quot;se&quot;&gt;\n&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// 2
&lt;/span&gt;    &lt;span class=&quot;n&quot;&gt;printf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;%s&lt;/span&gt;&lt;span class=&quot;se&quot;&gt;\n&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// 4
&lt;/span&gt;    &lt;span class=&quot;n&quot;&gt;printf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;%s&lt;/span&gt;&lt;span class=&quot;se&quot;&gt;\n&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// 5
&lt;/span&gt;    &lt;span class=&quot;n&quot;&gt;printf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;%s&lt;/span&gt;&lt;span class=&quot;se&quot;&gt;\n&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// 6
&lt;/span&gt;    &lt;span class=&quot;n&quot;&gt;printf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;%s&lt;/span&gt;&lt;span class=&quot;se&quot;&gt;\n&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// 7
&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;



&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;But your boss comes back with a change from the client.  They actually want to be able to specify how many times it prints.  So your boss suggests that a loop might help.  Now you&amp;#39;ve got serious trouble.  So you jump online and search for a loop.  Here&amp;#39;s an accepted answer that looks promising: &lt;a href=&quot;http://stackoverflow.com/a/3477439&quot;&gt;http://stackoverflow.com/a/3477439&lt;/a&gt;.&lt;/p&gt;

&lt;p&gt;Let&amp;#39;s see the code that will impress your boss.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;printmanyTimes&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;char&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;size_t&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;len&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;times&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// ensure null termination
&lt;/span&gt;    &lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;len&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;jmp_buf&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;buf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;

    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;setjmp&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;buf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;times&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;printf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;%s&lt;/span&gt;&lt;span class=&quot;se&quot;&gt;\n&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// 7
&lt;/span&gt;        &lt;span class=&quot;n&quot;&gt;longjmp&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;buf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt; 
    &lt;span class=&quot;nl&quot;&gt;http:&lt;/span&gt;&lt;span class=&quot;c1&quot;&gt;//stackoverflow.com/a/3477439
&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;

&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Notice how the power of C let&amp;#39;s you paste your link right into your function so you can document the source of the loop code you&amp;#39;re using.  That&amp;#39;s some forward thinking on the part of the language designers.&lt;/p&gt;

&lt;p&gt;Now your code can print as many times as your boss wants and if anyone asks how it works, you can kindly direct them to line 12.  No plagiarism, no problems #tripleairhorn.&lt;/p&gt;

&lt;h3 id=&quot;the-loop-anyone-can-read&quot;&gt;The Loop Anyone Can Read&lt;/h3&gt;

&lt;p&gt;So your clients just dropped another head scratcher on your desk.  You&amp;#39;ve got to double the contents of an entire array:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;doubleMyArray&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;arr&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;size_t&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;len&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// double every element    
&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;After a bit of trial and error, you&amp;#39;ve concluded that normal multiplication isn&amp;#39;t what you&amp;#39;re after, then you remember the printing problem.  Aha! This calls for a loop.  But hold on there, we don&amp;#39;t want to just copy-paste the loop we found before.  That&amp;#39;s old hat.  And some of your coworkers wanted you to teach them how it worked.  No one has time for distractions like that.  Time for a new trick.&lt;/p&gt;

&lt;p&gt;You already know about &lt;code&gt;while&lt;/code&gt; but you&amp;#39;re wishing it were simpler.  Think about all those times you forgot to mess with the condition variable and all the wasted hours waiting in vain for your program to finish.  Let me introduce you to the only &lt;code&gt;while&lt;/code&gt; you&amp;#39;ll ever use: the down-to-while.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;doubleMyArray&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;arr&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;size_t&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;len&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// double every element
&lt;/span&gt;    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;len&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;while&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;--&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// while i goes down to 0, brilliant!
&lt;/span&gt;        &lt;span class=&quot;n&quot;&gt;arr&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;// done, baby
&lt;/span&gt;        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The designers of the C language understood the complex nature of looping control flow (loop code, for short).  That&amp;#39;s why they included an operator just for loops that makes it clear to anyone what&amp;#39;s going on.  The down-to operator &lt;code&gt;--&amp;gt;&lt;/code&gt; is handy because it&amp;#39;s totally clear what&amp;#39;s going on.  Now the next time your coworkers ask for an explanation, you can laugh and say &amp;quot;While &lt;code&gt;i&lt;/code&gt; goes down to 0.  Duh.&amp;quot;.&lt;/p&gt;

&lt;h3 id=&quot;arrays-aren-39-t-picky&quot;&gt;Arrays Aren&amp;#39;t Picky&lt;/h3&gt;

&lt;p&gt;You see arrays a lot in code.  I think I use them almost every time I write a code.  And I bet, like me, you&amp;#39;ve been confused when someone gives you an &lt;code&gt;int *&lt;/code&gt; and tells you it&amp;#39;s &amp;quot;just an array&amp;quot;.  Yeah?  Then where&amp;#39;s the &lt;code&gt;[]&lt;/code&gt;, huh buddy?  Fear not.  They&amp;#39;re actually not wrong, despite how confusing it might seem.  But when dealing with these arrays-in-pointers clothing, it might be easy to get confused.  Normally in code like this, it&amp;#39;s easy to get something out of an array:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;myArr&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[];&lt;/span&gt;

&lt;span class=&quot;n&quot;&gt;myArr&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;5&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;];&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;It&amp;#39;s clear from the declaration that the way you access the array is with the &lt;code&gt;[]&lt;/code&gt;.  You can even copy the whole shebang and just fill in the &lt;code&gt;[]&lt;/code&gt; part.  But does the same hold true for these &lt;code&gt;int*&lt;/code&gt; things?&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;myArr2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;

&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;myArr25&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;  &lt;span class=&quot;c1&quot;&gt;// ?
&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;5&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;myArr2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;  &lt;span class=&quot;c1&quot;&gt;// ?
&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;5&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;myArr2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;  &lt;span class=&quot;c1&quot;&gt;// ?
&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;5&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;5&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;myArr2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// ????
&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;There&amp;#39;s got to be a better way.  And there is.  It turns out, you can actually use (as you may have noticed in some of the code for previous tricks) the &lt;code&gt;[]&lt;/code&gt; just the same.  But without the copy-paste opportunity, it may be difficult to remember exactly what to do.  Never fear.  Once again, the C people saw this one coming.  That&amp;#39;s why the &lt;code&gt;[]&lt;/code&gt; is so flexible.  What do I mean?  Let me show you:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;myArr3&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;

&lt;span class=&quot;n&quot;&gt;myArr3&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;5&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;];&lt;/span&gt;  &lt;span class=&quot;c1&quot;&gt;// 👍
&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;5&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;myArr3&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;];&lt;/span&gt;  &lt;span class=&quot;c1&quot;&gt;// also 👍
&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;You don&amp;#39;t even need to worry about where to put those brackets.  As long as you remember that they separate the first and second parts (they go around the second part), you&amp;#39;re good.  C&amp;#39;s got you covered.  Never fear the pointer again.&lt;/p&gt;

&lt;h3 id=&quot;getting-internal-with-extern&quot;&gt;Getting Internal With Extern&lt;/h3&gt;

&lt;p&gt;There are times where, despite your best effort, you need code that is not your own.  We&amp;#39;ve seen this already. Sometimes, though, it&amp;#39;s not code you have access to directly.  Let&amp;#39;s look at a mock real world example.&lt;/p&gt;

&lt;p&gt;You&amp;#39;ve got a library that your company is licensing for a ton of money.  The eggheads behind this baby are something else.  In this library (you know this because you go drinking with a guy who use to work at the company that makes it) there&amp;#39;s a special number they use that makes a ton of their calculations faster.  Now, everyone knows that this is the secret sauce of this company and you&amp;#39;ve got to pay them to taste it.  Every time you call any codes that use this number, their library records it and it goes on your monthly licensing bill.  But your boss thinks &lt;em&gt;you&lt;/em&gt; can do better.  And he&amp;#39;s right.&lt;/p&gt;

&lt;p&gt;This is where &lt;code&gt;extern&lt;/code&gt; comes in.  You may have seen this keyword used already to let you give others access to your code from a header file while keeping the implementation safely away from prying eyes in your .c file (or better yet, a .dll).  But &lt;code&gt;extern&lt;/code&gt; has another use.  It can actually be used to pull things directly into your code from elsewhere.  Let&amp;#39;s take a look:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Code.c
&lt;/span&gt;&lt;span class=&quot;cp&quot;&gt;#include &amp;lt;expensiveLib.h&amp;gt;
&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;// let's grab their magic constant.
// Your friend let you know the variable they store it in is called finvsqc (wtf lol?)
&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;extern&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;finvsqc&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;

&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;main&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;argc&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;char&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;argv&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[])&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;printf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;%d&lt;/span&gt;&lt;span class=&quot;se&quot;&gt;\r\n&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;finvsqc&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// 1597463007 (what's so special about this number?) Oh well
&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Even though the clever folks at the library company didn&amp;#39;t put any mention of &lt;code&gt;finvsqc&lt;/code&gt; in any of their header files, you can still reach right in and grab it if you know the name.  You&amp;#39;ve just saved your company money and made your boss look like a hero to the CFO.  Nice job.&lt;/p&gt;

&lt;h1 id=&quot;objective-c-structure-beyond-structs&quot;&gt;Objective-C: Structure Beyond Structs&lt;/h1&gt;

&lt;p&gt;Long ago in the history of computing, the idea of Objects was invented.  Data storage with specialized methods defined on them.  And with objects came inheritance: the ability to make more complex versions of an object or change its behavior by creating a modified version that inherited from the original.  It wasn&amp;#39;t long after that these ideas were brought to C at the language level.  Although, not C itself.  Like the concept of objects, languages were designed that inherited from C and added functionality (like Objects).  Two notable examples of this are C++ and Objective-C.  &lt;/p&gt;

&lt;h2 id=&quot;the-runtime-won-39-t-even-see-you-coming&quot;&gt;The Runtime Won&amp;#39;t Even See You Coming&lt;/h2&gt;

&lt;p&gt;Although Objective-C was invented later than C++, I&amp;#39;ll be going over my Objective-C tricks first.  These will be shorter than the C tricks because you may be unfamiliar with these languages so there&amp;#39;s no need to add the confusion of a story problem.&lt;/p&gt;

&lt;h3 id=&quot;context-is-everything&quot;&gt;Context Is Everything&lt;/h3&gt;

&lt;p&gt;Think of this trick as a conceptual bridge between the C tricks above and Objective-C.  The trick itself applies to C just as well, but really shines in Objective-C.  You&amp;#39;ll see what I mean.&lt;/p&gt;

&lt;p&gt;In Objective-C and more specifically, the Foundation libraries provided by Apple, there are a host of methods which take a &amp;quot;context&amp;quot; argument to help you keep multiple calls and callbacks straight. A call to one of these might look like this:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-objc&quot; data-lang=&quot;objc&quot;&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;foo&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;addObserver&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;self&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;forKeyPath&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;@&quot;bar&quot;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;options&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;:&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;context&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;:&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;...];&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Don&amp;#39;t mind the brackets, that&amp;#39;s just the way object methods are called.  The Objective-C designers opted for this type of method call because it makes the code read like english and is therefore &amp;quot;self-documenting&amp;quot;.  Neat.&lt;/p&gt;

&lt;p&gt;In the snippet above you can see we left the &lt;code&gt;context&lt;/code&gt; argument blank.  Well, you have to specify something.  According to Apple, &lt;code&gt;context&lt;/code&gt; is:&lt;/p&gt;

&lt;blockquote&gt;
&lt;p&gt;Arbitrary data that is passed to &lt;code&gt;anObserver&lt;/code&gt; in &lt;code&gt;observeValueForKeyPath:ofObject:change:context:&lt;/code&gt;.&lt;/p&gt;
&lt;/blockquote&gt;

&lt;p&gt;So what do we use if our use case has no context, or is context-free if you will.  The designers of Objective-C knew you&amp;#39;d ask that and they have the perfect context for you to use in this case: &lt;code&gt;free&lt;/code&gt;.  You can just go ahead and type &lt;code&gt;free&lt;/code&gt; so Objective-C knows you don&amp;#39;t want to use a context:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-objc&quot; data-lang=&quot;objc&quot;&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;foo&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;addObserver&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;self&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;forKeyPath&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;@&quot;bar&quot;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;options&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;:&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;context&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;:&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;free&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;];&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;How&amp;#39;s that for self documenting?  Anyone who is reading this code will instantly know that you don&amp;#39;t care about the context in this case and your observing is context-free.&lt;/p&gt;

&lt;h3 id=&quot;can-i-see-your-id&quot;&gt;Can I See Your ID&lt;/h3&gt;

&lt;p&gt;In Objective-C, all objects inherit from &lt;code&gt;NSObject&lt;/code&gt;. So if you want to define a function that takes in an object, it works like this:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-objc&quot; data-lang=&quot;objc&quot;&gt;&lt;span class=&quot;n&quot;&gt;BOOL&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;isObject&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;NSObject&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;object&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;object&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Alternatively, the language adds a new keyword &lt;code&gt;id&lt;/code&gt; which just means object.  So you can transform the above function into:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-objc&quot; data-lang=&quot;objc&quot;&gt;&lt;span class=&quot;n&quot;&gt;BOOL&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;isObject&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;id&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;object&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;object&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Check that out.  Think of the keystroke savings, and as a bonus you don&amp;#39;t even have to worry about the &lt;code&gt;*&lt;/code&gt; at all.  But the true benefits are yet to come.  Let&amp;#39;s say I  have this class:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-objc&quot; data-lang=&quot;objc&quot;&gt;&lt;span class=&quot;k&quot;&gt;@interface&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;NumberTracker&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;NSObject&lt;/span&gt;

&lt;span class=&quot;k&quot;&gt;@property&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;nonatomic&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;id&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;delegate&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;@property&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;nonatomic&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;NSNumber&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;trackedNumber&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;

&lt;span class=&quot;k&quot;&gt;@end&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;It&amp;#39;s great for tracking numbers, but as you may have heard, computers don&amp;#39;t understand money numbers.  Well, not normally.  The authors of the Foundation library understood this and created a class that could help us out: &lt;code&gt;NSDecimalNumber&lt;/code&gt;. It&amp;#39;s like &lt;code&gt;NSNumber&lt;/code&gt; but for decimal number systems like currency.  Let&amp;#39;s use it to make our money tracker:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-objc&quot; data-lang=&quot;objc&quot;&gt;&lt;span class=&quot;k&quot;&gt;@interface&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;MoneyTracker&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;NumberTracker&lt;/span&gt;

&lt;span class=&quot;k&quot;&gt;@property&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;nonatomic&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;id&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;delegate&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;@property&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;nonatomic&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;NSDecimalNumber&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;trackedMoney&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;

&lt;span class=&quot;k&quot;&gt;@end&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;But in the implementation, we want to have the &lt;code&gt;trackedMoney&lt;/code&gt; property use the same storage as the old &lt;code&gt;trackedNumber&lt;/code&gt; to save memory.  If we did this, the compiler would complain:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-objc&quot; data-lang=&quot;objc&quot;&gt;&lt;span class=&quot;k&quot;&gt;@implementation&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;MoneyTracker&lt;/span&gt;

&lt;span class=&quot;k&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;instancetype&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;init&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;self&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;super&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;init&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;];&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;  &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;self&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;_trackedNumber&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;[[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;NSDecimalNumber&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;alloc&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;init&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;];&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;self&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;NSDecimalNumber&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;trackedMoney&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;self&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;trackedNumber&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;];&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// compiler warning
&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;setTrackedMoney&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;:&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;NSDecimalNumber&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;trackedMoney&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;self&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;setTrackedNumber&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;trackedMoney&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;];&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;k&quot;&gt;@end&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;But we &lt;em&gt;know&lt;/em&gt; that it&amp;#39;s an &lt;code&gt;NSDecimalNumber&lt;/code&gt;.  Fortunately you can use the handy &lt;code&gt;id&lt;/code&gt; keyword to tell the compiler that you know what you&amp;#39;re doing:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-objc&quot; data-lang=&quot;objc&quot;&gt;&lt;span class=&quot;k&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;NSDecimalNumber&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;trackedMoney&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;self&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;trackedNumber&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;];&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// take a step back, compiler, I got this
&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;It&amp;#39;s that simple and you&amp;#39;ve eliminated another warning.&lt;/p&gt;

&lt;h1 id=&quot;c-the-evolution&quot;&gt;C++: The Evolution&lt;/h1&gt;

&lt;p&gt;C++ is an entirely different animal than C.  It looks like C at first glance but you&amp;#39;ll start to notice lots of &lt;code&gt;&amp;lt;&amp;gt;&lt;/code&gt; and &lt;code&gt;&amp;lt;&amp;lt;&lt;/code&gt; and &lt;code&gt;::&lt;/code&gt;.  C++ is C on another level (hence the name).  It adds objects and classes and a whole host of other things that make it a wonderful, powerful successor to the ubiquitous C for those brave enough to undertake learning it.  Since we looked at subclassing in the Objective-C tricks section, I thought it was worth mentioning the &lt;em&gt;even more powerful&lt;/em&gt; subclassing you can do in C++.  This is the only C++ trick I&amp;#39;ll be offering today, but it should get you on the right road if you&amp;#39;re just starting of in C++ development.&lt;/p&gt;

&lt;h2 id=&quot;a-taste-of-change&quot;&gt;A Taste of Change&lt;/h2&gt;

&lt;p&gt;C++ takes object orientedness to an entirely new level by allowing your classes to inherit from &lt;em&gt;multiple&lt;/em&gt; parent classes.  That&amp;#39;s right.  You can inherit the functionality and member variables of more than once class at a time.  Let&amp;#39;s take a dive into how this works.&lt;/p&gt;

&lt;p&gt;Your boss comes to you with a new color receipt printer and an SDK for it.  The SDK method you have to call is:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c++&quot; data-lang=&quot;c++&quot;&gt;&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;printColoredString&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;PrinterString&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;PrinterColor&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;clr&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;But you already have code to run the old SDK for the black and white printers that takes just a string:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c++&quot; data-lang=&quot;c++&quot;&gt;&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;printString&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;PrinterString&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;str&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Rather than add another list of colors that you have to keep consistent with your existing string list, bask in the glory of the C++ designers&amp;#39; wisdom and leverage multiple inheritance.  You simply need to create a drop-in replacement for &lt;code&gt;string&lt;/code&gt; that you can use in &lt;em&gt;both&lt;/em&gt; SDK versions.  But what would that look like?  Like this:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c++&quot; data-lang=&quot;c++&quot;&gt;&lt;span class=&quot;k&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;PrintableString&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;PrinterString&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;PrinterColor&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// everything is already implemented by the individual classes. C++ WIN!
&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;};&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Now that you have that all set, you only have to make a minor modification to the way you use the SDK:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c++&quot; data-lang=&quot;c++&quot;&gt;&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;internal_stringPrint&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;vector&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;PrintableString&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;strings&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;strings&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;();&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;printsdk&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;::&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;printsdk&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;version&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mf&quot;&gt;2.0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;c1&quot;&gt;// new code
&lt;/span&gt;            &lt;span class=&quot;n&quot;&gt;printsdk&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;::&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;printColoredString&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;strings&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;],&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;strings&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]);&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;c1&quot;&gt;// old code
&lt;/span&gt;            &lt;span class=&quot;n&quot;&gt;printsdk&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;::&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;printString&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;strings&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;i&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]);&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;That conversion is so simple.  And if any functionality gets added, you can just add to &lt;code&gt;PrintableString&lt;/code&gt; and add another case to &lt;code&gt;internal_stringPrint&lt;/code&gt;.  C++ is powerful.&lt;/p&gt;

&lt;h1 id=&quot;c-you-later&quot;&gt;C You Later&lt;/h1&gt;

&lt;p&gt;Now that you&amp;#39;ve gotten a taste of the things that make C (and its descendants) so  great, I hope you&amp;#39;re filled with the same passionate feelings that this code inspires in anyone who encounters it.  Thanks for reading all the way to then end.&lt;/p&gt;

&lt;p&gt;&lt;center&gt;
&lt;img src=&quot;/img/posts/thumbs-up.jpg&quot; alt=&quot;success&quot;&gt;
&lt;/center&gt;&lt;/p&gt;

&lt;style&gt;
img { 
  max-width:  500px; 
  display: inline-block;
}
&lt;/style&gt;
</description>
        <pubDate>Fri, 15 Jul 2016 00:00:00 -0600</pubDate>
        <link>http://www.pixio.com/blog/2016-07-15/c-considered-awesome/</link>
        <guid isPermaLink="true">http://www.pixio.com/blog/2016-07-15/c-considered-awesome/</guid>
        
        <category>c</category>
        
        <category>c++</category>
        
        <category>objective-c</category>
        
        <category>best practices</category>
        
        <category>coding</category>
        
        <category>awesome</category>
        
        <category>success</category>
        
        <category>seo</category>
        
        <category>tags</category>
        
        <category>low level</category>
        
        <category>software</category>
        
        <category>hardware</category>
        
        <category>computer</category>
        
        <category>thoughts</category>
        
        <category>ideas</category>
        
        <category>good</category>
        
        <category>great</category>
        
        
        <category>programming</category>
        
      </item>
    
      <item>
        <title>How to score big with Android's NDK</title>
        <description>&lt;p&gt;We have an unhealthy love for Rocket League here at Pixio, but our games usually end up looking like this:&lt;/p&gt;

&lt;p&gt;&lt;center&gt;
&lt;img src=&quot;/img/posts/ndk/cat-rocket-league.gif&quot; alt=&quot;Cat Picture&quot;&gt;
&lt;/center&gt;&lt;/p&gt;

&lt;p&gt;This is exactly what most people feel like when they first dive into the &lt;a href=&quot;https://developer.android.com/ndk/index.html&quot;&gt;Android Native Deveolpment Kit (NDK)&lt;/a&gt;. At I/O 2015 Google announced better support for the Android NDK and these improvements have made native development easier than ever before. Let&amp;#39;s go through some quick examples to see how to set up your code to take advantage of the new NDK support provided by Android Studio.&lt;/p&gt;

&lt;h2 id=&quot;quick-background&quot;&gt;Quick Background&lt;/h2&gt;

&lt;p&gt;The Android NDK is a set of tools that let you use C and C++ code in your Android application. It uses the &lt;a href=&quot;https://en.wikipedia.org/wiki/Java_Native_Interface&quot;&gt;Java Native Interface (JNI)&lt;/a&gt; which allows Java code interop with C/C++ code. While most projects will be better suited to only use Java, some projects such as games, physics simulators, or anything that requires lots of CPU could benefit from using the NDK. Additionally, applications which use shared C/C++ libraries will benefit.&lt;/p&gt;

&lt;h2 id=&quot;the-changes&quot;&gt;The Changes&lt;/h2&gt;

&lt;p&gt;Google made big changes when the switch from Eclipse to the current IntelliJ backed Android Studio. It brought improved features and a better environment to develop Android applications. With the &lt;a href=&quot;https://plus.google.com/+jetbrains/posts/P61rd5DnNK2&quot;&gt;announcement&lt;/a&gt; at I/O 2015, Google integrated &lt;a href=&quot;https://www.jetbrains.com/clion/&quot;&gt;CLion&lt;/a&gt;, the Jetbrains C/C++ IDE, into Android Studio to provide much better support for NDK development. This change brought things like code completion, refactoring, debugging, and many other features to make developing with C and C++ in Android applications much easier. This year they continued to add on to this new experience by adding the ability to support pre-existing NDK projects that used ndk-build or CMake rather than Gradle. Also, the new updates allows the programmer to use a single debugger for both the Java and C/C++ code in a project, streamlining the debugging process.&lt;/p&gt;

&lt;h2 id=&quot;setup&quot;&gt;Setup&lt;/h2&gt;

&lt;p&gt;We&amp;#39;re going to use some of the most up to date tools to gain the most benefit out of the recent changes to the Android NDK. Currently the enhanced NDK support is not in the stable channel, so we will be using the 2.2 preview 4 version of Android Studio and the 0.7.2 version of the Experimental Gradle plugin.&lt;/p&gt;

&lt;h3 id=&quot;android-studio&quot;&gt;Android Studio&lt;/h3&gt;

&lt;p&gt;First let&amp;#39;s download and setup Android Studio. Since we are using a Canary version of Android Studio, Google recommends installing it alongside your stable version of Android Studio instead of replacing it. You can find the download &lt;a href=&quot;http://tools.android.com/download/studio/builds/2-2-preview-4&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;

&lt;h3 id=&quot;create-android-project&quot;&gt;Create Android Project&lt;/h3&gt;

&lt;p&gt;Now that we have Android Studio setup and running, lets create a new project for our example. Let&amp;#39;s call our project &lt;code&gt;Android NDK Example&lt;/code&gt;.&lt;/p&gt;

&lt;p&gt;&lt;img src=&quot;/img/posts/ndk/new1.png&quot; alt=&quot;New Android Project&quot;&gt;
&lt;img src=&quot;/img/posts/ndk/new2.png&quot; alt=&quot;New Android Project&quot;&gt;
&lt;img src=&quot;/img/posts/ndk/new3.png&quot; alt=&quot;New Android Project&quot;&gt;
&lt;img src=&quot;/img/posts/ndk/new4.png&quot; alt=&quot;New Android Project&quot;&gt;&lt;/p&gt;

&lt;h3 id=&quot;install-ndk-package&quot;&gt;Install NDK Package&lt;/h3&gt;

&lt;p&gt;Before we can write any code we need to install and configure the NDK. Open the SDK Manager and browse to the SDK Tools tab. Find the NDK and check the box next to it. Hit apply or OK to start the download. &lt;/p&gt;

&lt;p&gt;&lt;img src=&quot;/img/posts/ndk/sdk-ndk.png&quot; alt=&quot;NDK install example&quot;&gt;&lt;/p&gt;

&lt;p&gt;Installing the NDK can take a long time. It is a large download (&amp;gt;1GB) so make sure you have a fast connection. While you&amp;#39;re waiting read a book, take a nap, or go play some Rocket League (my personal choice).&lt;/p&gt;

&lt;p&gt;Once the NDK package has been installed, we need to make sure our project knows where to find it. Ensure that your project structure points to the correct NDK package.&lt;/p&gt;

&lt;p&gt;&lt;img src=&quot;/img/posts/ndk/ndklocation.png&quot; alt=&quot;NDK install location&quot;&gt;&lt;/p&gt;

&lt;h3 id=&quot;configure-project&quot;&gt;Configure Project&lt;/h3&gt;

&lt;p&gt;Now that we have our project created and the NDK Package configured, let&amp;#39;s get our project ready for some native code. First let&amp;#39;s edit the project gradle file. We need to tell it we are going to use the experimental gradle plugin. Let&amp;#39;s change the classpath line for gradle to say this:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-&quot; data-lang=&quot;&quot;&gt;classpath 'com.android.tools.build:gradle-experimental:0.7.2'
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Next let&amp;#39;s edit the app module gradle file. The DSL has changed with the experimental gradle plugin so we need to update our app&amp;#39;s gradle.&lt;/p&gt;

&lt;p&gt;Here&amp;#39;s a quick summary of the changes:
* We change the plugin from &lt;code&gt;com.android.application&lt;/code&gt; to &lt;code&gt;com.android.model.application&lt;/code&gt;
* The &lt;code&gt;android&lt;/code&gt; block is nested in a &lt;code&gt;model&lt;/code&gt; block
* We add &lt;code&gt;.apiLevel&lt;/code&gt; to &lt;code&gt;minSdkVersion&lt;/code&gt; and &lt;code&gt;targetSdkVersion&lt;/code&gt; &lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-&quot; data-lang=&quot;&quot;&gt;apply plugin: 'com.android.model.application'

model {
    android {
        compileSdkVersion 23
        buildToolsVersion &quot;23.0.2&quot;
        defaultConfig {
            applicationId &quot;com.example.androidndkexample&quot;
            minSdkVersion.apiLevel 21
            targetSdkVersion.apiLevel 23
            versionCode 1
            versionName &quot;1.0&quot;
            testInstrumentationRunner &quot;android.support.test.runner.AndroidJUnitRunner&quot;
        }
        buildTypes {
            release {
                minifyEnabled false
                proguardFiles.add(file('proguard-android.txt'))
            }
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:23.4.0'
    compile 'com.android.support.constraint:constraint-layout:1.0.0-alpha3'
    testCompile 'junit:junit:4.12'
}
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Now that we have gradle set up properly with the experimental version, let&amp;#39;s add the bit we need so we can write some NDK code.&lt;/p&gt;

&lt;p&gt;After &lt;code&gt;buildTypes&lt;/code&gt; in the android block, let&amp;#39;s add this NDK block:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-&quot; data-lang=&quot;&quot;&gt;model {
    android {
        //...
        ndk {
            moduleName = &quot;ndk-example-jni&quot;
        }
    }
}
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;This tells Android Studio that we want a module named &lt;code&gt;ndk-example-jni&lt;/code&gt; which will allow us to interface between Java and C/C++. Do a gradle sync and we will be ready to write some code.&lt;/p&gt;

&lt;h2 id=&quot;demo&quot;&gt;Demo&lt;/h2&gt;

&lt;h3 id=&quot;creating-and-calling-jni-functions&quot;&gt;Creating and Calling JNI Functions&lt;/h3&gt;

&lt;p&gt;Since we have an unhealthy relationship with playing Rocket League here at Pixio, let&amp;#39;s create a &lt;code&gt;Player&lt;/code&gt; class so that we can mimic playing the game and displaying our stats. This example isn&amp;#39;t to show off the speed of the Android NDK, but to give an example of setting up your code and using some of the new features provided by the new NDK support in Android Studio.
For our &lt;code&gt;Player&lt;/code&gt; class, let&amp;#39;s create it with four member variables: &lt;code&gt;goals&lt;/code&gt;, &lt;code&gt;shots&lt;/code&gt;, and &lt;code&gt;assists&lt;/code&gt;. These will be our stats from playing the game. For now our class should look like this:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;Player&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;goals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shots&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;assists&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;Player&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(){&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;goals&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shots&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;assists&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//Getters and Setters&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;In this class we need to let Android know that we want to load our NDK module. We&amp;#39;ll write a static system call to load the &lt;code&gt;ndk-example-jni&lt;/code&gt; library into our class.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;Player&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;System&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;loadLibrary&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;ndk-example-jni&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;This tells Android to load the NDK module so we can call native functions. Now it&amp;#39;s time for the magic of the new Android Studio NDK support to come into play. First define a function in the Player class that we want to call on the C side, let&amp;#39;s call it &lt;code&gt;shoot()&lt;/code&gt;.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;Player&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;boolean&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;shoot&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Now we can let Android Studio create the native C method stub by placing the cursor over &lt;code&gt;shoot()&lt;/code&gt;, pressing &lt;code&gt;Alt&lt;/code&gt; + &lt;code&gt;Enter&lt;/code&gt;, and then selecting &lt;code&gt;Create function Java_com_example_androidndkexample_Player_shoot&lt;/code&gt;.&lt;/p&gt;

&lt;video src=&quot;/img/posts/ndk/ndk-autocomplete.webm&quot; loop=true autoplay=true&gt;&lt;/video&gt;

&lt;p&gt;This will create a folder at &lt;code&gt;src/main/jni&lt;/code&gt; and place a new file called &lt;code&gt;ndk-example-jni.c&lt;/code&gt; with our new native function in it.&lt;/p&gt;

&lt;p&gt;&lt;img src=&quot;/img/posts/ndk/jnifolder.png&quot; alt=&quot;New File Location&quot;&gt;&lt;/p&gt;

&lt;p&gt;Notice how the method signature must follow this exact pattern. It starts with the package name followed by the class name and the Java function name. This method signature is what allows the Java Native Interface to connect the Java and C/C++ code. &lt;/p&gt;

&lt;p&gt;Let&amp;#39;s fill in this newly created function.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;cp&quot;&gt;#include &amp;lt;jni.h&amp;gt;
&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;JNIEXPORT&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jboolean&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;JNICALL&lt;/span&gt;
&lt;span class=&quot;nf&quot;&gt;Java_com_example_androidndkexample_Player_shoot&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;JNIEnv&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//Get a reference to the shots member variable field
&lt;/span&gt;    &lt;span class=&quot;n&quot;&gt;jclass&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;cls&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetObjectClass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shot_field_id&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;cls&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;shots&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;I&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//Get and set shots in Player class
&lt;/span&gt;    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shots&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetIntField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shot_field_id&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;shots&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;SetIntField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shot_field_id&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shots&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//For now we never score
&lt;/span&gt;    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Look at that! We&amp;#39;re accessing and modifying the Java object that called this native function. All we need is a class and field reference to be able to get and set member variables inside the calling class. The way Java represents objects is vastly different than in C or C++. That is why we need the jclass and jfieldID. It gives us a window into the Java class allowing us to reference and modify variables in the class from our C or C++ code. This is really powerful!&lt;/p&gt;

&lt;p&gt;You may have noticed the jboolean and jobject types. These are types that are used to take a Java type and convert it into something that can be used in C or C++ code. Other types include jint, jlong, jbyte, and so on. This allows us to have native euquivalents to our Java primitive types.&lt;/p&gt;

&lt;p&gt;Another thing to notice is the last parameter to the &lt;code&gt;GetIntField&lt;/code&gt; function. In this example, we pass in &amp;quot;I&amp;quot;. This may seem arbitrary at first but this is how we tell the function that we want to reference a variable that is an int. There are letters that reference different types. For example &amp;quot;F&amp;quot; is for float, &amp;quot;D&amp;quot; is for double, and &amp;quot;I&amp;quot; is for integer. A full list of all the type signatures and primitive types can be found in &lt;a href=&quot;http://docs.oracle.com/javase/7/docs/technotes/guides/jni/spec/types.html&quot;&gt;Oracle&amp;#39;s documentation&lt;/a&gt; for the JNI.&lt;/p&gt;

&lt;p&gt;Let&amp;#39;s display some data now that we have the ability to take some shots. We&amp;#39;ll create some buttons to shoot and pass as well as three TextViews to display our player statistics. Let that creativity flow and create a beautiful interface!&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;MainActivity&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;AppCompatActivity&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;implements&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;View&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;OnClickListener&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Player&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;mPlayer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;protected&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onCreate&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Bundle&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;savedInstanceState&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;onCreate&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;savedInstanceState&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;setContentView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;layout&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;activity_main&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

        &lt;span class=&quot;c1&quot;&gt;//TextView and Button setup code&lt;/span&gt;

        &lt;span class=&quot;n&quot;&gt;mPlayer&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Player&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onClick&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;View&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;v&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;switch&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;v&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;getId&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;())&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;case&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;pass_button&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;:&lt;/span&gt;
                &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;case&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;shoot_button&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;:&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;mPlayer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;shoot&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;updateStats&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
                &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
                &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;It&amp;#39;s great to see the shot counter go up, but we want to start scoring goals. When we shoot, there should be a chance to score a goal. Let&amp;#39;s set up a new folder in the root of our project folder and call it &lt;code&gt;external&lt;/code&gt;. We&amp;#39;re going to place some C files in there and reference them through the C search path. We need to modify our app gradle file to do this.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-&quot; data-lang=&quot;&quot;&gt;model {
    android {
        //...
        ndk {
            moduleName = &quot;ndk-example-jni&quot;
            CFlags.add(&quot;-std=gnu99&quot;)
            //Search Path
            CFlags.add(&quot;-I${file(&quot;../external&quot;)}&quot;.toString())
        }
        sources {
            main {
                jni {
                    source {
                        srcDirs = [&quot;src/main/jni&quot;, &quot;../external&quot;]
                    }
                }
            }
        }
    }
}
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Notice how we have added the search path to our CFlags and set up the source directories. The project will have a default source directory of &lt;code&gt;src/main/jni&lt;/code&gt; but we can either move it or specify multiple locations to build.&lt;/p&gt;

&lt;p&gt;Now that we have added our external folder, let&amp;#39;s put two files in it. We&amp;#39;ll call them &lt;code&gt;gameRandomness.h&lt;/code&gt; and &lt;code&gt;gameRandomness.c&lt;/code&gt;. These randomness files are really basic, but it gives an example of how to use and reference external C or C++ libraries, something we can&amp;#39;t do without the NDK. &lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;cp&quot;&gt;#ifndef ANDROIDNDKEXAMPLE_GAMERANDOMNESS_H
#define ANDROIDNDKEXAMPLE_GAMERANDOMNESS_H
&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;passBecameAssist&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;();&lt;/span&gt;

&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shotBecameGoal&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;();&lt;/span&gt;

&lt;span class=&quot;cp&quot;&gt;#endif //ANDROIDNDKEXAMPLE_GAMERANDOMNESS_H
&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;cp&quot;&gt;#include &amp;lt;time.h&amp;gt;
#include &amp;lt;stdlib.h&amp;gt;
&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;playerActionWorked&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(){&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;srand&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;time&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nb&quot;&gt;NULL&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;));&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;rand&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;%&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;2&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;passBecameAssist&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(){&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;playerActionWorked&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;();&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shotBecameGoal&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(){&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;playerActionWorked&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;();&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;These will be some random functions for our player actions to call. Let&amp;#39;s call one by adding a pass function to our Player class. If a player passes, there should be a chance that they will gain an assist. That&amp;#39;s not how assists work, but we want everyone to feel like they are helping, regardless of their true lack of contribution! We need to update our different files to let this happen.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;Player&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;pass&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Note that we need to include our new C header in our jni file to be able to use the random functions we just created.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;cp&quot;&gt;#include &amp;lt;gameRandomness.h&amp;gt;
&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;JNIEXPORT&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;JNICALL&lt;/span&gt;
&lt;span class=&quot;nf&quot;&gt;Java_com_example_androidndkexample_Player_pass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;JNIEnv&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;passBecameAssist&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()){&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;//Get a reference to the shots member variable field
&lt;/span&gt;        &lt;span class=&quot;n&quot;&gt;jclass&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;cls&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetObjectClass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;assist_field_id&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;cls&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;assists&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;I&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

        &lt;span class=&quot;c1&quot;&gt;//Get and set assists in Player class
&lt;/span&gt;        &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;assists&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetIntField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;assist_field_id&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;assists&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;SetIntField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;assist_field_id&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;assists&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;MainActivity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onClick&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;View&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;v&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;switch&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;v&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;getId&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;())&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;case&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;pass_button&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;:&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;mPlayer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;pass&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;updateStats&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
                &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
            &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;If we run our app we can see that pushing the pass button only updates the assists counter part of the time. This is exactly what we wanted. We can add the same chance functionality to the shot button.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;n&quot;&gt;JNIEXPORT&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jboolean&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;JNICALL&lt;/span&gt;
&lt;span class=&quot;nf&quot;&gt;Java_com_example_androidndkexample_Player_shoot&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;JNIEnv&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//Get a reference to the shots member variable field
&lt;/span&gt;    &lt;span class=&quot;n&quot;&gt;jclass&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;cls&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetObjectClass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shot_field_id&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;cls&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;shots&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;I&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//Get and set shots in Player class
&lt;/span&gt;    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shots&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetIntField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shot_field_id&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;shots&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;SetIntField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shot_field_id&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shots&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//See if we scored
&lt;/span&gt;    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;shotBecameGoal&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()){&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;jfieldID&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;goal_field_id&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetFieldID&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;cls&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;goals&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;I&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

        &lt;span class=&quot;c1&quot;&gt;//Get and set goals in Player class
&lt;/span&gt;        &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;goals&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;GetIntField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;goal_field_id&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;goals&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;SetIntField&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;goal_field_id&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;goals&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h3 id=&quot;passing-and-receiving-data&quot;&gt;Passing and Receiving Data&lt;/h3&gt;

&lt;p&gt;So far we&amp;#39;ve been able to shoot and pass. Now let&amp;#39;s add some functionality to let the user know the result of their Player actions. We will need to add a TextView to display the status and return strings from our native functions to display to the user. We will also need to change the return values of the methods for the Player class.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;Player&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;shoot&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;pass&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;save&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;n&quot;&gt;JNIEXPORT&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jstring&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;JNICALL&lt;/span&gt;
&lt;span class=&quot;nf&quot;&gt;Java_com_example_androidndkexample_Player_shoot&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;JNIEnv&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//...
&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;shotBecameGoal&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()){&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;//...
&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;NewStringUTF&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;Nice shot! Nice shot! Nice shot!&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;NewStringUTF&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;Close one...&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;n&quot;&gt;JNIEXPORT&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jstring&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;JNICALL&lt;/span&gt;
&lt;span class=&quot;nf&quot;&gt;Java_com_example_androidndkexample_Player_pass&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;JNIEnv&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;passBecameAssist&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()){&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;//...
&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;NewStringUTF&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;Pass became an assist!&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;NewStringUTF&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;Player passed the ball.&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;When we run this we can now see the result of our attempts to shoot or pass. There are many things that you can receive and return from native functions. These can be simple things like primitives all the way up to full Java objects. You can even call member functions from the calling class. The Android NDK can be a very powerful tool once you overcome the steep learning curve.&lt;/p&gt;

&lt;h3 id=&quot;logging-and-debugging&quot;&gt;Logging and Debugging&lt;/h3&gt;

&lt;p&gt;Let&amp;#39;s add one more thing to our app. When our Player shoots, the Player should shoot with a certain power value. If the power value is greater than 4, the shot will score no matter what. Otherwise the shot will score based off of our random values. Here&amp;#39;s the code we need to change to do this.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;Player&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;native&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;shoot&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;power&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;c1&quot;&gt;//...
&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shotBecameGoal&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;power&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//...
&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;c1&quot;&gt;//...
&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shotBecameGoal&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;power&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;){&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;power&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;4&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;||&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;playerActionWorked&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;();&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//...
&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;n&quot;&gt;JNIEXPORT&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jstring&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;JNICALL&lt;/span&gt;
&lt;span class=&quot;nf&quot;&gt;Java_com_example_androidndkexample_Player_shoot&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;JNIEnv&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jint&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;power&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//...
&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;shotBecameGoal&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;power&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)){&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;//...
&lt;/span&gt;    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//...
&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;MainActivity&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;AppCompatActivity&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;implements&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;View&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;OnClickListener&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onClick&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;View&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;v&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;switch&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;v&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;getId&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;())&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;case&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;shoot_button&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;:&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;Random&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;r&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Random&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
                &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;power&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;r&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;nextInt&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;10&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;shotResult&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;Shot with power &quot;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;power&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;: &quot;&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;mPlayer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;shoot&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;power&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;updateStats&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
                &lt;span class=&quot;n&quot;&gt;updatePlayerStatusText&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;shotResult&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
                &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
            &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Great! Now that our player can shoot with different power values, let&amp;#39;s look at how we can view that power value. First we can set breakpoints in our Java and C/C++ code. When we run the app in debug mode we can stop the execution of the code and inspect the variables and environments in both the Java and C/C++ code. It may take some time to get used to jumping between Java and C/C++ when stepping through the code with the debugger, but it is a powerful tool to use to find out what is happening as your code executes.&lt;/p&gt;

&lt;p&gt;What if you want to log data to the Android log from your C/C++ code? The NDK has you covered on this. All you have to do is import the Android log header file and call the log print function and your log messages will show up in the Android log.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;cp&quot;&gt;#include &amp;lt;android/log.h&amp;gt;
&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;JNIEXPORT&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jstring&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;JNICALL&lt;/span&gt;
&lt;span class=&quot;nf&quot;&gt;Java_com_example_androidndkexample_Player_shoot&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;JNIEnv&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;env&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jobject&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;instance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;jint&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;power&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;

    &lt;span class=&quot;kt&quot;&gt;char&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;buffer&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;100&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;];&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;snprintf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;buffer&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;100&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;Player shot with a power of %d.&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;power&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;__android_log_print&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ANDROID_LOG_DEBUG&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;AndroidNDKExample-JNI&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;buffer&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//...
&lt;/span&gt;    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;shotBecameGoal&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;power&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)){&lt;/span&gt;

        &lt;span class=&quot;n&quot;&gt;__android_log_print&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ANDROID_LOG_DEBUG&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;AndroidNDKExample-JNI&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;Player's shot became a goal.&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

        &lt;span class=&quot;c1&quot;&gt;//...
&lt;/span&gt;    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;c1&quot;&gt;//...
&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The log print function allows you to specify the log level, a tag, and a message to print just like you can in Java. This can be another great tool for building and debugging your NDK application.&lt;/p&gt;

&lt;h2 id=&quot;conclusion&quot;&gt;Conclusion&lt;/h2&gt;

&lt;p&gt;The Android NDK can be a bit of a daunting task at first, but once you get the basic concepts down it can be a very powerful tool for your applications. A lot of projects will not need to use the NDK, but knowing how to use the NDK gives you much greater flexibility in your application allowing more 3rd party libraries and more shared codebases. With the recent updates to Android Studio to better suppor the NDK, harnessing the power and speed of native development has never been easier.&lt;/p&gt;

&lt;p&gt;&lt;center&gt;
&lt;video src=&quot;/img/posts/ndk/dave.webm&quot; loop=true autoplay=true&gt;&lt;/video&gt;
&lt;/center&gt;&lt;/p&gt;

&lt;p&gt;You can find the demo project &lt;a href=&quot;https://github.com/williamshupe/AndroidNDKExample&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;
</description>
        <pubDate>Fri, 08 Jul 2016 00:00:00 -0600</pubDate>
        <link>http://www.pixio.com/blog/2016-07-08/how-to-score-big-with-androids-ndk/</link>
        <guid isPermaLink="true">http://www.pixio.com/blog/2016-07-08/how-to-score-big-with-androids-ndk/</guid>
        
        <category>android</category>
        
        <category>java</category>
        
        <category>ndk</category>
        
        <category>android studio</category>
        
        
        <category>programming</category>
        
      </item>
    
      <item>
        <title>Hey Siri: What can you do?</title>
        <description>&lt;p&gt;WWDC 2016 is now over and we saw all sorts of cool new things. The majority of changes introduced by Apple include things like Photos and Maps updates which help these products better compete with Google’s offerings. One of the standout announcements for developers is the opening up of core functionality to developers including lock screen extensions, map extensions, and Siri extensions. This marks a change at the world’s most valuable company which is opening up the platform more than it has ever done so in the past.&lt;/p&gt;

&lt;h2 id=&quot;journey-into-the-darkness&quot;&gt;Journey into the Darkness&lt;/h2&gt;

&lt;p&gt;Let’s take a journey into the murky waters of beta software! For this example, we’re going to add the ability to make payments and receive payments within our application. I have a (fake) bitcoin wallet application which has no users. Of course it has no users, it doesn’t have Siri integration! Now is the perfect time to fix that.&lt;/p&gt;

&lt;p&gt;We will begin with &lt;a href=&quot;https://developer.apple.com/sirikit/&quot;&gt;SiriKit&lt;/a&gt;. No, I&amp;#39;m not talking about &lt;a href=&quot;https://en.wikipedia.org/wiki/Sirikit&quot;&gt;Queen Sirikit&lt;/a&gt;. SiriKit is actually two frameworks: &lt;a href=&quot;https://developer.apple.com/reference/intents&quot;&gt;Intents&lt;/a&gt; and &lt;a href=&quot;https://developer.apple.com/reference/intentsui&quot;&gt;Intents UI&lt;/a&gt;. These two frameworks allow you to create a Siri enabled extension (as well as MapKit extensions).&lt;/p&gt;

&lt;p&gt;Intents are objects which encapsulate information that describes an action. When you open up Siri and ask it to “Call Mom,” you are generating an intent which the system resolves by opening the dialer and calling your mother. This same basic principle applies to your SiriKit enabled extension. Siri parses your voice input and generates an intent which is handed off to your application to be handled appropriately.&lt;/p&gt;

&lt;p&gt;Let&amp;#39;s begin by opening up the new Xcode 8 and adding a new target of type &lt;strong&gt;Intents Extension&lt;/strong&gt;. There are a couple setup steps that must occur before we get into the code itself.&lt;/p&gt;

&lt;p&gt;First, the application in which the extension is embedded must request permission to use Siri. This behavior is identical to most permissioned resources on iOS such as the camera and microphone.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-swift&quot; data-lang=&quot;swift&quot;&gt;&lt;span class=&quot;kt&quot;&gt;INPreferences&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;requestSiriAuthorization&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;status&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;in&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// Handle authorization if necessary&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The other task is to modify the &lt;code&gt;Info.plist&lt;/code&gt; for the Siri extension. Add any intents you wish your application to handle into the &lt;code&gt;IntentsSupported&lt;/code&gt; array nested within the &lt;code&gt;NSExtension&lt;/code&gt; dictionary.&lt;/p&gt;

&lt;p&gt;We&amp;#39;re ready to implement the logic for our Siri extension now. Open up the &lt;code&gt;IntentHandler.swift&lt;/code&gt; and clean out the existing methods. The only method left should be the &lt;code&gt;handler(for:)&lt;/code&gt; method. Additionally, remove all those protocols for which the class conforms to. Replace the protocol conformance with the &lt;code&gt;INSendPaymentIntentHandling&lt;/code&gt; protocol.&lt;/p&gt;

&lt;p&gt;Let&amp;#39;s pause and take a look at the &lt;a href=&quot;https://developer.apple.com/reference/intents/insendpaymentintenthandling&quot;&gt;INSendPaymentIntentHandling&lt;/a&gt; protocol. There are 4 &amp;quot;resolve&amp;quot; methods, one &amp;quot;confirm&amp;quot; method, and one &amp;quot;handle&amp;quot; method. Only the &lt;code&gt;handle(sendPayment:completion:)&lt;/code&gt; method is required. This protocol maps directly to how a conversation is handled with Siri. The user begins by making a request of Siri which resolves it. If not enough information is provided, Siri will ask for clarification and the input(s) will be resolved until the user&amp;#39;s intent is fully understood. The request is then confirmed (if necessary) and then it&amp;#39;s actually performed (or handled). This incredibly simple protocol perfectly defines the way your users have conversations with Siri. Amazing!&lt;/p&gt;

&lt;p&gt;The resolution step is important to ensure that we have enough information as well as the right information. If we are sending bitcoins to Robert and we don&amp;#39;t have his wallet address, we can&amp;#39;t send him money. Handling this case is really simple! We just have to take in the input, determine if the input contains enough information to fulfill the request, and return the corresponding result.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-swift&quot; data-lang=&quot;swift&quot;&gt;&lt;span class=&quot;kd&quot;&gt;func&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;resolvePayee&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;forSendPayment&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;intent&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;INSendPaymentIntent&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;with&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;completion&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;INPersonResolutionResult&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Swift&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;Void&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;guard&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;let&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;payee&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;intent&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;payee&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;nf&quot;&gt;completion&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;INPersonResolutionResult&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;needsValue&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;())&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;let&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;resolutionResult&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;INPersonResolutionResult&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;let&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;_&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Wallet&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;walletAddress&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;forUser&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;payee&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;displayName&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;resolutionResult&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;INPersonResolutionResult&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;success&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;with&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;payee&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;resolutionResult&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;INPersonResolutionResult&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;needsMoreDetails&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;for&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;payee&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;nf&quot;&gt;completion&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;resolutionResult&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;We don&amp;#39;t need a payment method, so let&amp;#39;s explicitly mark it as not required. Doing so, Siri will ignore any payment method information. This is not strictly necessary as not implementing the method will produce the same result, but let&amp;#39;s be pedantic here.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-swift&quot; data-lang=&quot;swift&quot;&gt;&lt;span class=&quot;kd&quot;&gt;func&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;resolvePaymentMethod&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;forSendPayment&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;intent&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;INSendPaymentIntent&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;with&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;completion&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;INPaymentMethodResolutionResult&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Swift&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;Void&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;nf&quot;&gt;completion&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;INPaymentMethodResolutionResult&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;notRequired&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;())&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;What happens if the user doesn&amp;#39;t have enough money in their wallet? We can resolve that step before we actually send. Our &lt;code&gt;resolveCurrencyAmount(forSendPayment:with:)&lt;/code&gt; will look something like this:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-swift&quot; data-lang=&quot;swift&quot;&gt;&lt;span class=&quot;k&quot;&gt;let&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;resolutionResult&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;INCurrencyAmountResolutionResult&lt;/span&gt;

&lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;let&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;amount&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;intent&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;currencyAmount&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;let&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;bitcoinAmount&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;amount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;amount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;convertToBitcoin&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;from&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;amount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;currencyCode&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;where&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Wallet&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;canSpend&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;bitcoinAmount&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;resolutionResult&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;INCurrencyAmountResolutionResult&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;success&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;with&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;amount&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;resolutionResult&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;INCurrencyAmountResolutionResult&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;unsupported&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;with&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;notNow&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;alternativeCurrencyAmounts&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;INCurrencyAmount&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;amount&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Wallet&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;currentBalance&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;currencyCode&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;s&quot;&gt;&quot;BTC&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)])&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;resolutionResult&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;INCurrencyAmountResolutionResult&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;needsValue&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;nf&quot;&gt;completion&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;resolutionResult&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The logic here is simple enough. Convert the intended amount to bitcoin and determine if that amount is payable with the given funds of the wallet. If not enough money is provided, offer the full contents of the wallet as an alternative.&lt;/p&gt;

&lt;blockquote&gt;
&lt;p&gt;Note: SiriKit and iOS 10 are still in Beta. At this time, the &lt;code&gt;unsupported&lt;/code&gt; method as well as other non-success methods such as &lt;code&gt;confirmationRequired&lt;/code&gt; and &lt;code&gt;disambiguation&lt;/code&gt; do not initiate the correct response from Siri.&lt;/p&gt;
&lt;/blockquote&gt;

&lt;p&gt;We&amp;#39;ve now resolved all the inputs and we&amp;#39;re also sure they&amp;#39;re valid. It&amp;#39;s time to confirm that the payment will work. Here we can also adjust the values. If the user requests Siri to send &amp;quot;100 dollars&amp;quot; to someone, we may convert the dollar amount to Bitcoin. Additionally, we could factor in the latest exchange rates and lock those in as well as account for any transaction fees if necessary. This step can be treated like a dry run of the request to ensure that it would be properly handled.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-swift&quot; data-lang=&quot;swift&quot;&gt;&lt;span class=&quot;kd&quot;&gt;func&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;confirm&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;sendPayment&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;intent&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;INSendPaymentIntent&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;completion&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;INSendPaymentIntentResponse&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;Swift&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;Void&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// TODO: Convert price to bitcoin so the user sees exactly how much will be removed&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;let&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;resolutionResult&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;INSendPaymentIntentResponse&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;nv&quot;&gt;code&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;success&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;nf&quot;&gt;completion&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;resolutionResult&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Once the user confirms the payment, we just need to follow through with the request by actually handling it. This would probably take the form of an API call in this example. There could also be the case where you require your users to authenticate in the application. In that case, rather than returning a response code of &lt;code&gt;.success&lt;/code&gt;, you could instead call the completion with the &lt;code&gt;.failureRequiringAppLaunch
&lt;/code&gt; response code which would then open up your application and you could finish the flow in that way.&lt;/p&gt;

&lt;h2 id=&quot;show-me-the-money&quot;&gt;Show Me the Money!&lt;/h2&gt;

&lt;p&gt;Requesting money with Bitcoin is a more complicated process. We could initiate a request that sends an e-mail or a text message. We could initiate a request on our server for which that other user could log in and accept or reject our request. However if the other party is in the same room, it can be easier to simply generate a payment request which includes your wallet address, the amount, and a message if necessary. This can then be displayed as a QR code for the payee to scan and send payment to, regardless of whether or not they are registered with our server. Fear not, friends. It&amp;#39;s easier than you think.&lt;/p&gt;

&lt;p&gt;Start off adding &lt;code&gt;INRequestPaymentIntent&lt;/code&gt; to the &lt;code&gt;IntentsSupported&lt;/code&gt; array in the &lt;code&gt;Info.plist&lt;/code&gt;. Then, implement the &lt;a href=&quot;https://developer.apple.com/reference/intents/inrequestpaymentintenthandling&quot;&gt;INRequestPaymentIntentHandling&lt;/a&gt; protocol. Implementing this happens much the same way we implemented the protocol to support sending a payment. Resolve all of the intent parameters and confirm the intent request. How do we handle the request? If we have a payer (recipient of the payment request), we can send the request through our server. If no recipient is specified, we will always succeed because the QR code is displayed on the screen.&lt;/p&gt;

&lt;p&gt;Our logic for handling the intent is done. Now we just need to present the QR code. If you didn&amp;#39;t check the box to include an Intent UI Extension, now is a great time to add that new target to you application. The first thing to do is add the &lt;code&gt;INRequestPaymentIntent&lt;/code&gt; key to the &lt;code&gt;IntentsSupported&lt;/code&gt; array in the &lt;code&gt;Info.plist&lt;/code&gt; for the UI extension.&lt;/p&gt;

&lt;p&gt;The UI extension is a simple view controller with a storyboard in which you can setup your interface. Simply pull the parameters from that intent in order to generate the interface you wish to display. This is done in the configure method.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-swift&quot; data-lang=&quot;swift&quot;&gt;&lt;span class=&quot;k&quot;&gt;guard&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;let&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;intent&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;interaction&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;intent&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;as?&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;INRequestPaymentIntent&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;nf&quot;&gt;completion&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;zero&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;c1&quot;&gt;// Parse parameters&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;var&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;params&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;String&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]()&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;let&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;note&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;intent&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;note&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;params&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;message&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;note&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;let&lt;/span&gt; &lt;span class=&quot;nv&quot;&gt;amount&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;intent&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;currencyAmount&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;?&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;nf&quot;&gt;getBitcoinAmount&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;params&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;amount&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;amount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;amount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;description&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;c1&quot;&gt;// Generate QR code from the intent request parameters&lt;/span&gt;

&lt;span class=&quot;c1&quot;&gt;// Update our view&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;imageView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;image&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;qrcodeImage&lt;/span&gt;

&lt;span class=&quot;c1&quot;&gt;// Call the completion&lt;/span&gt;
&lt;span class=&quot;nf&quot;&gt;completion&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;desiredSize&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;And that&amp;#39;s it! The &lt;code&gt;Info.plist&lt;/code&gt; links up the intent extension with the intent UI extension for you and displays it. You&amp;#39;re free to add whatever you wish to your view and animate it if you so choose. If we don’t want to show any custom UI if we handle the case by sending a server request, we can call the completion with a zero size.&lt;/p&gt;

&lt;p&gt;It is important to note that the UI extension is totally non-interactive so you are unable to enter a pin number or adjust a slider value within your UI extension. In order to accomplish this user experience, you will have to adjust your handle method in the Siri extension to return a success status of &lt;code&gt;.failureRequiringAppLaunch&lt;/code&gt;. Then, your application will continue the flow of the user request.&lt;/p&gt;

&lt;h2 id=&quot;i-m-sorry-dave-i-m-afraid-i-can-t-do-that&quot;&gt;I’m Sorry, Dave, I’m afraid I can’t do that.&lt;/h2&gt;

&lt;p&gt;While it is really exciting to see Apple open up access to functionality such as Siri, it still is rather restrictive. Currently the domains are restricted to messaging, voip calling, ride booking, payments, workouts, photo search, and CarPlay. While this is certainly disappointing, it makes sense from Apple’s perspective. This model allows Siri to be fast and places abounds on the amount of ambiguity it is required to handle. Additionally, it makes for a really simple developer experience that mimics a real conversation.&lt;/p&gt;

&lt;p&gt;But I &lt;em&gt;really&lt;/em&gt; wanted to order a pizza with Siri. Unfortunately, it&amp;#39;s just not possible... or is it? No. Not right now. But there are alternatives. The easy and hacky alternative is to pigeonhole your Siri interactions into one of the existing domains. Sending a payment with a note &lt;em&gt;could&lt;/em&gt; work, but it doesn&amp;#39;t make a lot of sense and does not provide a good user experience.&lt;/p&gt;

&lt;p&gt;Luckily, iOS 10 also introduced the &lt;a href=&quot;https://developer.apple.com/reference/speech&quot;&gt;Speech&lt;/a&gt; framework which allows you to easily recognize speech and convert that audio to text. You could then take the parsed text and run it through Apple&amp;#39;s &lt;a href=&quot;https://developer.apple.com/library/ios/documentation/Cocoa/Reference/NSLinguisticTagger_Class/&quot;&gt;NSLinguisticTagger&lt;/a&gt; to get relavant tags and parts of speech. This gives you way more control over the ability to parse the user input but requires much more work to capture the intent of the user’s words. This is made far more confusing when localization and internationalization are taken into consideration. It is also possible to employ 3rd party libraries such as Nuance&amp;#39;s &lt;a href=&quot;https://developer.nuance.com/&quot;&gt;SpeechKit 2&lt;/a&gt; framework which may fit your needs better than SiriKit.&lt;/p&gt;

&lt;h2 id=&quot;i-39-m-sorry-i-didn-39-t-get-that&quot;&gt;I&amp;#39;m sorry, I didn&amp;#39;t get that.&lt;/h2&gt;

&lt;p&gt;SiriKit is still in beta and it shows. With iOS 10 not launching until late 2016, there&amp;#39;s still plenty of time to fix issues. While it is exciting that Apple is opening up their platform, it remains confined to the way Apple wants these interactions to occur. Not only are they restricting which domains from which you can integrate your app with Siri, but they are also restricting some of the interactions. For example, you can define custom vocabulary for workouts in your application, but you are unable to define custom vocabulary for payment types or currencies. This restriction denies developers from sending in-app currencies such as coins. Developers are also unable to respond with errors that are more descriptive. The error message received by the user when they don’t have enough funds is incredibly vague.&lt;/p&gt;

&lt;p&gt;These restrictions are not made without reason. Doing so lets Apple to open up Siri while still allowing users to interact without being forced to learn new interactions for each application. The opening up of this and other core functionality is quite welcome enabling a richer experience for users that extends beyond just the installed app. Perhaps one day in the not too distant future Siri will understand our great desire for pizza and know what to do in that situation.&lt;/p&gt;

&lt;p&gt;The full demo project is available &lt;a href=&quot;https://github.com/kwongius/SiriKitExample&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;
</description>
        <pubDate>Fri, 17 Jun 2016 00:00:00 -0600</pubDate>
        <link>http://www.pixio.com/blog/2016-06-17/hey-siri-what-can-you-do/</link>
        <guid isPermaLink="true">http://www.pixio.com/blog/2016-06-17/hey-siri-what-can-you-do/</guid>
        
        <category>ios</category>
        
        <category>ios10</category>
        
        <category>siri</category>
        
        <category>sirikit</category>
        
        <category>swift</category>
        
        
        <category>programming</category>
        
      </item>
    
      <item>
        <title>Let's Code: Reduce, Reuse, RecyclerView</title>
        <description>&lt;p&gt;If you’re still using &lt;a href=&quot;https://developer.android.com/reference/android/widget/ListView.html&quot;&gt;ListView&lt;/a&gt; in Android, boy have I got a treat for you! Today, I wanted to talk about one of my favorite UI components in the Android SDK, &lt;a href=&quot;https://developer.android.com/reference/android/support/v7/widget/RecyclerView.html&quot;&gt;RecyclerView&lt;/a&gt;, which is basically a ListView. RecyclerView is used to display rows (or grids) of items to the end user from some dataset. Built in to the RecyclerView are animations for adding, deleting, and moving items in the list, so we get all of that material design goodness with some simple API calls.&lt;/p&gt;

&lt;p&gt;The main difference between a RecyclerView and a List View is the use of the view holder design pattern. This pattern makes use of view holders which bind their data into &amp;#39;recyclable&amp;#39; views. A view becomes &amp;#39;recycled&amp;#39; when it is scrolled off screen and will try to be used again by another view holder such that only the views that ever need to be on screen are created. This helps to improve the efficiency of your application, especially when scrolling in the RecyclerView. A view holder class also holds onto references for the views that it will bind data to later. This is a performance boost the RecyclerView offers as you won&amp;#39;t need to find the view by id every time you want to update the UI for that view holder.&lt;/p&gt;

&lt;p&gt;In this silly little demo, let&amp;#39;s build an app that has a header, a place for a contact image, and then a bunch of information about said contact. We will also be able to add items to the adapter and remove them by receiving clicks in a view holder!&lt;/p&gt;

&lt;p&gt;Let&amp;#39;s start with a new project in Android Studio with just a blank activity and xml layout file. There is some setup to get a RecyclerView in and working, but it won&amp;#39;t take us very long. First, let&amp;#39;s fill out the XML file with a simple layout containing our RecyclerView:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-xml&quot; data-lang=&quot;xml&quot;&gt;&lt;span class=&quot;nt&quot;&gt;&amp;lt;RelativeLayout&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;xmlns:android=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;http://schemas.android.com/apk/res/android&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;&amp;gt;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;&amp;lt;android.support.v7.widget.RecyclerView&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:id=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@+id/recycler&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
        &lt;span class=&quot;nt&quot;&gt;/&amp;gt;&lt;/span&gt;
&lt;span class=&quot;nt&quot;&gt;&amp;lt;/RelativeLayout&amp;gt;&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Then in the activity, we need to set the layout manager and the adapter of our RecyclerView. Our app doesn&amp;#39;t require much, so we can use a simple &lt;code&gt;LinearLayoutManager&lt;/code&gt; to display our rows in a linear fashion.  When creating the layout manager, you can specify whether it should lay out vertically or horizontally, as well as if the order should be reversed (start at the bottom versus the top). Let’s create a bare bones adapter for now with a simple list that maintains all the data to be displayed.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;MainActivity&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;AppCompatActivity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;protected&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onCreate&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Bundle&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;savedInstanceState&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;onCreate&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;savedInstanceState&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;setContentView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;layout&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;activity_main&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

        &lt;span class=&quot;c1&quot;&gt;// Get the recycler view and set up the layout manager as well as the adapter&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;recycler&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;findViewById&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;recycler&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;recycler&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;recycler&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;setLayoutManager&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;LinearLayoutManager&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;MainActivity&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;recycler&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;setAdapter&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;MainRecyclerAdapter&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;());&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;MainRecyclerAdapter&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;Adapter&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;List&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;String&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;mInfoStrings&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

        &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;MainRecyclerAdapter&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;mInfoStrings&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ArrayList&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&amp;gt;();&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

        &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;ViewHolder&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onCreateViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ViewGroup&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;parent&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;viewType&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

        &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onBindViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;ViewHolder&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;holder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;position&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

        &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getItemCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;2&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;mInfoStrings&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// 2 = Header + Contact&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Next, let&amp;#39;s define some view types in &lt;code&gt;MainRecyclerAdapter&lt;/code&gt; to use in our RecyclerView. We will need a view type for the header holder, the contact holder, and the info holder. &lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;HEADER_TYPE&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CONTACT_TYPE&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;INFO_TYPE&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;2&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;In order to really make use of these view types, we also need to override the &lt;code&gt;getItemViewType()&lt;/code&gt; method in our adapter. This method will be used to determine which view type is at some position, and can help us when binding data to our view holders a little later on.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getItemViewType&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;position&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;position&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;HEADER_TYPE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;position&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CONTACT_TYPE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;INFO_TYPE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Great! Now that we have the view types supported, let&amp;#39;s define them with some simple layouts xml layouts:&lt;/p&gt;

&lt;p&gt;&lt;code&gt;holder_header.xml&lt;/code&gt;&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-xml&quot; data-lang=&quot;xml&quot;&gt;&lt;span class=&quot;nt&quot;&gt;&amp;lt;LinearLayout&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;xmlns:android=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;http://schemas.android.com/apk/res/android&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:orientation=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;vertical&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;wrap_content&quot;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;&amp;gt;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;&amp;lt;TextView&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:id=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@+id/holder_header_text_view&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;wrap_content&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_marginStart=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/activity_horizontal_margin&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_marginEnd=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/activity_horizontal_margin&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:textSize=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/header_text_size&quot;&lt;/span&gt;
        &lt;span class=&quot;nt&quot;&gt;/&amp;gt;&lt;/span&gt;
&lt;span class=&quot;nt&quot;&gt;&amp;lt;/LinearLayout&amp;gt;&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;&lt;code&gt;holder_contact.xml&lt;/code&gt;&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-xml&quot; data-lang=&quot;xml&quot;&gt;&lt;span class=&quot;nt&quot;&gt;&amp;lt;RelativeLayout&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;xmlns:android=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;http://schemas.android.com/apk/res/android&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;wrap_content&quot;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;&amp;gt;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;&amp;lt;ImageView&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:id=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@+id/holder_contact_image_view&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/contact_image_size&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:scaleType=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;centerCrop&quot;&lt;/span&gt;
        &lt;span class=&quot;nt&quot;&gt;/&amp;gt;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;&amp;lt;TextView&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:id=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@+id/holder_contact_name_view&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;wrap_content&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:gravity=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;center_horizontal&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_alignParentBottom=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;true&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:textSize=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/contact_name_text_size&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:textColor=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@color/white&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:background=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@drawable/black_bottom_gradient&quot;&lt;/span&gt;
        &lt;span class=&quot;nt&quot;&gt;/&amp;gt;&lt;/span&gt;
&lt;span class=&quot;nt&quot;&gt;&amp;lt;/RelativeLayout&amp;gt;&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;&lt;code&gt;holder_info.xml&lt;/code&gt;&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-xml&quot; data-lang=&quot;xml&quot;&gt;&lt;span class=&quot;nt&quot;&gt;&amp;lt;RelativeLayout&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;xmlns:android=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;http://schemas.android.com/apk/res/android&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;wrap_content&quot;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;&amp;gt;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;&amp;lt;TextView&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:id=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@+id/holder_info_text_view&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;wrap_content&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_marginStart=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/activity_horizontal_margin&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_toStartOf=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@+id/holder_info_delete&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_centerVertical=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;true&quot;&lt;/span&gt;
        &lt;span class=&quot;nt&quot;&gt;/&amp;gt;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;&amp;lt;ImageView&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:id=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@+id/holder_info_delete&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/min_touch_size&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/min_touch_size&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_marginEnd=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/activity_horizontal_margin&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_alignParentEnd=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;true&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:src=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@android:drawable/ic_menu_delete&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:background=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;?attr/selectableItemBackground&quot;&lt;/span&gt;
        &lt;span class=&quot;nt&quot;&gt;/&amp;gt;&lt;/span&gt;
&lt;span class=&quot;nt&quot;&gt;&amp;lt;/RelativeLayout&amp;gt;&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Back in &lt;code&gt;MainActivity.java&lt;/code&gt;, lets define some classes for our view holders. &lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;MainActivity&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;AppCompatActivity&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;HeaderViewHolder&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;ViewHolder&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;

        &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;TextView&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;mHeaderTextView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

        &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;HeaderViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;View&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

            &lt;span class=&quot;n&quot;&gt;mHeaderTextView&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;TextView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;findViewById&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;holder_header_text_view&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;ContactViewHolder&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;ViewHolder&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;

        &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;TextView&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;mContactNameView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageView&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;mContactImageView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

        &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ContactViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;View&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

            &lt;span class=&quot;n&quot;&gt;mContactNameView&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;TextView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;findViewById&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;holder_contact_name_view&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;mContactImageView&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ImageView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;findViewById&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;holder_contact_image_view&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;InfoViewHolder&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;ViewHolder&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;

        &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;View&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;mDeleteView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;TextView&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;mInfoTextView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

        &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;InfoViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;View&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;

            &lt;span class=&quot;n&quot;&gt;mDeleteView&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;findViewById&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;holder_info_delete&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;mInfoTextView&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;TextView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;findViewById&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;holder_info_text_view&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;One last step to finish the setup of these view holders, we need to actually create them in our adapter&amp;#39;s &lt;code&gt;onCreateViewHolder()&lt;/code&gt;! This will be a cinch since we&amp;#39;ve already set up our view types.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;ViewHolder&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onCreateViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ViewGroup&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;parent&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;viewType&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;LayoutInflater&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;inflater&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;LayoutInflater&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;from&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;parent&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;getContext&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;());&lt;/span&gt;

    &lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;ViewHolder&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;holder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// Declare the ViewHolder to initialize later&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;switch&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;viewType&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;case&lt;/span&gt; &lt;span class=&quot;nl&quot;&gt;HEADER_TYPE:&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;holder&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;HeaderViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;inflater&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;inflate&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;layout&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;holder_header&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;parent&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;false&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;case&lt;/span&gt; &lt;span class=&quot;nl&quot;&gt;CONTACT_TYPE:&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;holder&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ContactViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;inflater&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;inflate&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;layout&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;holder_contact&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;parent&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;false&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;case&lt;/span&gt; &lt;span class=&quot;nl&quot;&gt;INFO_TYPE:&lt;/span&gt;
            &lt;span class=&quot;c1&quot;&gt;// Intentional overflow&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;default&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;:&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;holder&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;InfoViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;inflater&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;inflate&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;layout&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;holder_info&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;parent&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;false&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;holder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Now we&amp;#39;re finally ready to fill in the method &lt;code&gt;onBindViewHolder()&lt;/code&gt; in our &lt;code&gt;MainRecyclerAdapter&lt;/code&gt;. This method is responsible for updating the view holder’s UI components will the data that we need. By having public variables in our view holders, our adapter can directly control what those values display. Let&amp;#39;s go ahead and fill in some simple data so we can actually see something when we build the app. Notice the use of &lt;code&gt;getItemViewType()&lt;/code&gt; here which we wrote earlier to help us determine which view holder type we are trying to bind data to.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onBindViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;ViewHolder&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;holder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;position&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;switch&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;getItemViewType&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;position&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;))&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;case&lt;/span&gt; &lt;span class=&quot;nl&quot;&gt;HEADER_TYPE:&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;HeaderViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;holder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;).&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;mHeaderTextView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;setText&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;This is a title!&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;case&lt;/span&gt; &lt;span class=&quot;nl&quot;&gt;CONTACT_TYPE:&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ContactViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;holder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;).&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;mContactNameView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;setText&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;Person Name&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
            &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ContactViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;holder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;).&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;mContactImageView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;setImageResource&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;drawable&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;background&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;case&lt;/span&gt; &lt;span class=&quot;nl&quot;&gt;INFO_TYPE:&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;((&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;InfoViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;holder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;).&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;mInfoTextView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;setText&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;mInfoStrings&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;get&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;position&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;2&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
            &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Of course, we don&amp;#39;t have anything in our list yet so this is what should show up: (depending on the &lt;code&gt;background&lt;/code&gt; image you use)&lt;/p&gt;

&lt;p&gt;&lt;img src=&quot;/img/posts/recycler_image_simple.png&quot; alt=&quot;alt-text&quot;&gt;&lt;/p&gt;

&lt;p&gt;All right, now that we have a basic working RecyclerView! Before we go any further, let’s add a method to our &lt;code&gt;MainRecyclerAdapter&lt;/code&gt; that lets us insert strings to the dataset. We can make use of the built in insertion animations by using &lt;code&gt;notifyItemInserted()&lt;/code&gt; rather than just refreshing the whole list with &lt;code&gt;notifyDataSetChanged()&lt;/code&gt;.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;addInfoString&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;String&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;info&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;mInfoStrings&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;add&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;info&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// Notify an insert of the item into the end of the info section&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;notifyItemInserted&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;getItemCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;2&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// 2 = Header + Contact&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Let&amp;#39;s use a &lt;a href=&quot;https://material.google.com/components/buttons-floating-action-button.html&quot;&gt;Floating Action Button (or FAB)&lt;/a&gt; to add info rows to our RecyclerView. Here is the new &lt;code&gt;activity_main.xml&lt;/code&gt; that includes our FAB.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-xml&quot; data-lang=&quot;xml&quot;&gt;&lt;span class=&quot;cp&quot;&gt;&amp;lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&amp;gt;&lt;/span&gt;
&lt;span class=&quot;nt&quot;&gt;&amp;lt;RelativeLayout&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;xmlns:android=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;http://schemas.android.com/apk/res/android&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;&amp;gt;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;&amp;lt;android.support.v7.widget.RecyclerView&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:id=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@+id/recycler&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
        &lt;span class=&quot;nt&quot;&gt;/&amp;gt;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;&amp;lt;android.support.design.widget.FloatingActionButton&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/min_touch_size&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/min_touch_size&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_alignParentBottom=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;true&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_alignParentEnd=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;true&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_marginBottom=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/activity_vertical_margin&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:layout_marginEnd=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/activity_horizontal_margin&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:onClick=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;onFabClicked&quot;&lt;/span&gt;
        &lt;span class=&quot;na&quot;&gt;android:src=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@android:mipmap/sym_def_app_icon&quot;&lt;/span&gt;
        &lt;span class=&quot;nt&quot;&gt;/&amp;gt;&lt;/span&gt;
&lt;span class=&quot;nt&quot;&gt;&amp;lt;/RelativeLayout&amp;gt;&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Now that the view is in our layout, let&amp;#39;s hook it up with our &lt;code&gt;MainActivity&lt;/code&gt; and make a way to add data to the adapter.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onFabClicked&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;View&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;v&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;recycler&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;findViewById&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;id&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;recycler&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;recycler&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;MainRecyclerAdapter&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;adapter&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;MainRecyclerAdapter&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;recycler&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;getAdapter&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;adapter&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;adapter&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;addInfoString&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;Test Info&quot;&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Awesome! Now we have a way to add data to our RecyclerView. However, you may have noticed a problem. When the screen fills up with rows of information, we will have a row at the bottom of the screen that is covered up by our FAB. Oh no! &lt;/p&gt;

&lt;p&gt;&lt;img src=&quot;/img/posts/recycler_image_overlap.png&quot; alt=&quot;alt-text&quot;&gt;&lt;/p&gt;

&lt;p&gt;Don&amp;#39;t worry, we just have to add another view type to our adapter to account for having a FAB at the bottom of the screen.  Let&amp;#39;s just use a Space view for our footer that matches the size of our FAB. This will allow every row to always be visible.&lt;/p&gt;

&lt;p&gt;&lt;code&gt;holder_footer.xml&lt;/code&gt;&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-xml&quot; data-lang=&quot;xml&quot;&gt;&lt;span class=&quot;nt&quot;&gt;&amp;lt;Space&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;xmlns:android=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;http://schemas.android.com/apk/res/android&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_width=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;match_parent&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_height=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/min_touch_size&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_marginBottom=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/activity_vertical_margin&quot;&lt;/span&gt;
    &lt;span class=&quot;na&quot;&gt;android:layout_marginEnd=&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;@dimen/activity_horizontal_margin&quot;&lt;/span&gt;
    &lt;span class=&quot;nt&quot;&gt;/&amp;gt;&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;With that xml file defined, a class needs to be defined to hold this view type.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;FooterViewHolder&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;ViewHolder&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;FooterViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;View&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Now, we can create a new view type in our &lt;code&gt;MainRecyclerAdapter&lt;/code&gt; to represent this footer view type. Next, let&amp;#39;s update our &lt;code&gt;getItemViewType()&lt;/code&gt; method to find which position corresponds to this new type.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;static&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;final&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;FOOTER_TYPE&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;3&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;
&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getItemViewType&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;position&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// Get the footer position (the last item in the list)&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;footerPosition&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;getItemCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

    &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;position&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;HEADER_TYPE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;position&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;1&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;CONTACT_TYPE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;position&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;==&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;footerPosition&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;FOOTER_TYPE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;else&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;INFO_TYPE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;We also need to update our &lt;code&gt;onCreateViewHolder()&lt;/code&gt; method to create the new footer view type.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;k&quot;&gt;case&lt;/span&gt; &lt;span class=&quot;nl&quot;&gt;FOOTER_TYPE:&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;holder&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;FooterViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;inflater&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;inflate&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;layout&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;holder_footer&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;parent&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;false&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;));&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;break&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Lastly, we have to account for the size of our &lt;code&gt;MainRecyclerAdapter&lt;/code&gt; now that we have a new footer view type.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;getItemCount&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;3&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;mInfoStrings&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;size&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;();&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// 3 = Header + Contact + Footer&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Perfect.&lt;/p&gt;

&lt;p&gt;&lt;img src=&quot;/img/posts/recycler_image_overlap_fixed.png&quot; alt=&quot;alt-text&quot;&gt;&lt;/p&gt;

&lt;p&gt;To wrap up this demo, we need to set up the delete icons to actually delete that row. We will do this by creating a listener interface in our &lt;code&gt;MainActivity&lt;/code&gt; that our adapter will implement. This interface will take in the position that is being clicked so that it can remove the correct data and update the view accordingly.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;interface&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;OnViewHolderClickedListener&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onViewHolderClicked&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;position&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;When our &lt;code&gt;MainRecyclerAdapter&lt;/code&gt; implements this listener, we again will make use of the built in remove animation that the RecyclerView offers to us. By using &lt;code&gt;notifyItemRemoved()&lt;/code&gt;, our RecyclerView cleanly moves all necessary elements and removes the desired element.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;MainRecyclerAdapter&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;Adapter&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;implements&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;OnViewHolderClickedListener&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onViewHolderClicked&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;position&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;// Delete the data&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;mInfoStrings&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;remove&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;position&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;-&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;2&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// minus 2 for the header and contact&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;notifyItemRemoved&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;position&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt; &lt;span class=&quot;c1&quot;&gt;// Update UI&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;To hook this into to our &lt;code&gt;InfoViewHolder&lt;/code&gt;, we will require this interface type as a parameter in the constructor so that it can report it&amp;#39;s clicks to the adapter. Our &lt;code&gt;InfoViewHolder&lt;/code&gt; will also act as the click listener for our delete button so that it can report the it&amp;#39;s position to the interface listener when it needs to be deleted. &lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;class&lt;/span&gt; &lt;span class=&quot;nc&quot;&gt;InfoViewHolder&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;extends&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;RecyclerView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;ViewHolder&lt;/span&gt; &lt;span class=&quot;kd&quot;&gt;implements&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;View&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;OnClickListener&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;View&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;mDeleteView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;TextView&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;mInfoTextView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;private&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;WeakReference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;OnViewHolderClickedListener&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;mClickListener&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;;&lt;/span&gt;

    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;InfoViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;View&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;OnViewHolderClickedListener&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;listener&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;kd&quot;&gt;super&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;itemView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;c1&quot;&gt;//...&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;mDeleteView&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;setOnClickListener&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
        &lt;span class=&quot;n&quot;&gt;mClickListener&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;WeakReference&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;&amp;lt;&amp;gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;listener&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;

    &lt;span class=&quot;nd&quot;&gt;@Override&lt;/span&gt;
    &lt;span class=&quot;kd&quot;&gt;public&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;onClick&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;View&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;v&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;if&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;mClickListener&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;get&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;()&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;!=&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;null&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;mClickListener&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;get&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;().&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;onViewHolderClicked&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;getAdapterPosition&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;());&lt;/span&gt;
        &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;span class=&quot;o&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;It is important to use a &lt;code&gt;WeakReference&lt;/code&gt; to keep hold of the reference to the adapter, so that the reference is not retained longer than the adapter wants to be retained. This prevents retain cycles which can cause memory leaks in our application.&lt;/p&gt;

&lt;p&gt;Then we update &lt;code&gt;onCreateViewHolder()&lt;/code&gt; to pass the adapter as a listener when creating the &lt;code&gt;InfoViewHolder&lt;/code&gt;.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-java&quot; data-lang=&quot;java&quot;&gt;&lt;span class=&quot;n&quot;&gt;holder&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;new&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;InfoViewHolder&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;inflater&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;inflate&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;R&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;layout&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;.&lt;/span&gt;&lt;span class=&quot;na&quot;&gt;holder_info&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;parent&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kc&quot;&gt;false&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;),&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;this&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;);&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;And voila, we now have a RecyclerView set up with an adapter where we can add and remove rows &lt;em&gt;and&lt;/em&gt; takes into account the space used up by our FAB so that our bottom rows aren&amp;#39;t covered up. By using an interface, we were able to report communication up from a view holder to it&amp;#39;s parent adapter. Using the topics covered here, you should now be able to do just about anything you need with a RecyclerView.&lt;/p&gt;

&lt;p&gt;We didn’t cover how to use a &lt;a href=&quot;https://developer.android.com/reference/android/support/v7/widget/GridLayoutManager.html&quot;&gt;GridLayoutManager&lt;/a&gt;, which would make the RecyclerView behave similarly to a &lt;a href=&quot;https://developer.android.com/reference/android/widget/GridView.html&quot;&gt;GridView&lt;/a&gt;. Instead of laying out views in a single file line with the &lt;code&gt;LinearLayoutManager&lt;/code&gt;, the manager would layout views in columns to make a grid of view holders. Or, if you really want to get crazy, you could use a &lt;a href=&quot;https://developer.android.com/reference/android/support/v7/widget/StaggeredGridLayoutManager.html&quot;&gt;StaggeredGridLayoutManager&lt;/a&gt;, which will lay views out of varying height in columns to similar to what Pinterest does or the Google Keep app.&lt;/p&gt;

&lt;p&gt;Most apps use this view to accomplish varying tasks from simple lists of one view type (like a messages application) to sectionable lists that have many different types. A good example of this is the search in Spotify or Youtube that list different channels, playlists, and single pieces of media in one scrolling list. Typically, the best use case for a RecyclerView over a Scroll View is when the list will be modified while someone is using it. If all the data is static and won&amp;#39;t change, you&amp;#39;ll probably be better off with a Scroll View.&lt;/p&gt;

&lt;p&gt;As an extra exercise, try to convert the info view’s TextView into an EditText and store any new data into the adapter. &lt;/p&gt;

&lt;p&gt;Check out the final project &lt;a href=&quot;https://github.com/CalvinKern/RecyclerViewTest&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;
</description>
        <pubDate>Fri, 10 Jun 2016 00:00:00 -0600</pubDate>
        <link>http://www.pixio.com/blog/2016-06-10/reduce-reuse-recyclerview/</link>
        <guid isPermaLink="true">http://www.pixio.com/blog/2016-06-10/reduce-reuse-recyclerview/</guid>
        
        <category>android</category>
        
        <category>java</category>
        
        
        <category>programming</category>
        
      </item>
    
      <item>
        <title>C in the 21st Century</title>
        <description>&lt;p&gt;I love &lt;a href=&quot;https://en.wikipedia.org/wiki/C_(programming_language)&quot;&gt;C&lt;/a&gt;. The language is small, fast, and elegant, being the prime choice for many &lt;a href=&quot;https://www.opengl.org&quot;&gt;time-tested libraries&lt;/a&gt; in every corner of software development. It is one of the most portable languages that compiles to native executables. However, it lacks direct support for language features developers have come to depend on, particularly objects and closures. Developing software without the structure of objects is a foreign concept for the majority of developers. &lt;a href=&quot;https://en.wikipedia.org/wiki/Functional_programming&quot;&gt;Functional Programming&lt;/a&gt; has made a resurgence with the addition of closures to popular languages like C++, C#, Java, and Swift, but these all still make the assumption that &lt;a href=&quot;https://en.wikipedia.org/wiki/Object-oriented_programming&quot;&gt;Object Oriented Programming&lt;/a&gt; techniques are also available. So how can C be used to do clear, effort efficient, and even gasp FUN software development?&lt;/p&gt;

&lt;h2 id=&quot;c-can-be-object-oriented&quot;&gt;C Can Be Object Oriented&lt;/h2&gt;

&lt;p&gt;Contrary to popular belief, C is actually an OOP-friendly language. Using its structure definitions, and functions that operate on them, we can make objects with data and methods. Header files can be used to separate private object interfaces from public ones. Type systems can even be created that have all the features that objects in OOP-native languages have. Getting objects set up in C does take more effort, but it is not as much as you may think.&lt;/p&gt;

&lt;p&gt;Let’s look at what is involved in making objects in C.&lt;/p&gt;

&lt;h2 id=&quot;structs-and-functions&quot;&gt;Structs and Functions&lt;/h2&gt;

&lt;p&gt;The defining characteristic of OOP is in how to think about the data in a program and how it is manipulated. Rather than thinking of the data as a sea of bytes and functions that swim in that sea, OOP organizes the data into a packet that is manipulated using a defined interface. This usually takes the form of classes and methods, with the data in the class being encapsulated. We can create the same structure in C by using a structure to store the object’s data and functions that take the struct as one of their parameters to form the interface. Let’s build a simple image object, starting with the header file. We’ll add an implementation file later.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;cm&quot;&gt;/* image.h */&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;w&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;h&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pix&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;};&lt;/span&gt;

&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;img_make&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fill_clr&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;img_dstry&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;img_ptr&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;img_load&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;char&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;file_path&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;img_get_pix&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;img_ptr&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;img_set_pix&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;img_ptr&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pix&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;I can hear the complaints from here. &amp;quot;Gross!!! Look at all those *’s, tiny names with few vowels, blah_bleh junk, and struct and const words peppered everywhere. You can’t even guarantee int is 32-bits! This is why I use [language name] instead of C. I’m not doing my app development in this!&amp;quot; Similar complaints can follow, and you’re right!&lt;/p&gt;

&lt;h2 id=&quot;moving-beyond-traditional-c&quot;&gt;Moving Beyond Traditional C&lt;/h2&gt;

&lt;p&gt;Code written in C does not have to follow the conventions established in the 70’s. Using better naming techniques alone makes the experience much better. Using Pascal Case and Camel Case improves readability. Realizing that we all use a text editor with code completion, we can also use longer names, eliminating the need for less-readable short names.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;cm&quot;&gt;/* Image.h */&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixels&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;};&lt;/span&gt;

&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageCreate&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fillColor&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageDestroy&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;imagePointer&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageLoad&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;char&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;filePath&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageGetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;imagePointer&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageSetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;imagePointer&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h2 id=&quot;the-taming-of-the-int&quot;&gt;The Taming of the Int&lt;/h2&gt;

&lt;p&gt;The image object here stores pixel colors as integers. Because the range of an integer determines how many colors a pixel can take on in our image, we’d like to know what that is. The range of integer in a language is always a concern, but it is made worse in C because it is hardware and even compiler dependent.&lt;/p&gt;

&lt;p&gt;In order to solve this and other issues, &lt;a href=&quot;https://en.wikipedia.org/wiki/C99&quot;&gt;C99&lt;/a&gt; was created. Among many other improvements, C99 defines fixed sizes for integer types and allows declarations of variables anywhere in a function body, instead of just at the beginning. C11, a 2011 standard with more wonderful additions, is gaining broad support in compilers. For now, let’s use C99 to fix the integer size issue for pixels in our image.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Image.h
&lt;/span&gt;&lt;span class=&quot;cp&quot;&gt;#include &amp;lt;stdint.h&amp;gt;
&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;uint32_t&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixels&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;};&lt;/span&gt;

&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageCreate&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;uint32_t&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fillColor&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageDestroy&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;imagePointer&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageLoad&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;char&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;filePath&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;uint32_t&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageGetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;imagePointer&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageSetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;imagePointer&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;uint32_t&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h2 id=&quot;types-types-types&quot;&gt;Types, Types, Types&lt;/h2&gt;

&lt;p&gt;This 32-bit standard size integer will store exactly 32-bit pixels on any platform we compile the program for. It introduces an awkward &lt;code&gt;_t&lt;/code&gt; to the type name, but we get the exact precision we wanted. The stdint.h header even defines limits for the different integer types, like &lt;code&gt;UINT32_MAX&lt;/code&gt;.&lt;/p&gt;

&lt;p&gt;We don’t have to live with these names, though. Notice that width and height still use the int keyword, as we don’t have a specific need that the width and height have a particular range. The &lt;code&gt;uint32_t&lt;/code&gt; is only being used for the exact precision we need for pixels. If we use the &lt;code&gt;typedef&lt;/code&gt; keyword, we can rename &lt;code&gt;uint32_t&lt;/code&gt; to &lt;code&gt;Pixel&lt;/code&gt; and &lt;code&gt;struct Image&lt;/code&gt; to just &lt;code&gt;Image&lt;/code&gt;, making things here look even better.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Image.h
&lt;/span&gt;&lt;span class=&quot;cp&quot;&gt;#include &amp;lt;stdint.h&amp;gt;
&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;typedef&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;uint32_t&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixels&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;};&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;typedef&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;

&lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageCreate&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fillColor&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageDestroy&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;imagePointer&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageLoad&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;char&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;filePath&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageGetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;imagePointer&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageSetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;imagePointer&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h2 id=&quot;opaque-types&quot;&gt;Opaque Types&lt;/h2&gt;

&lt;p&gt;One feature that OOP languages support that we want in our C-based app is encapsulation. Encapsulation keeps the details of the way an object is made and manipulated separate from the interface others use to work with the object. In our example, the image width, height, and pixels in the image are directly accessible. We could change the width without allocating space for more pixels, leaving the object dangerously inconsistent state.&lt;/p&gt;

&lt;p&gt;In C, we can use the concept of an Opaque Type as a replacement for classes and gain encapsulation. An Opaque Type is a definition for a pointer to a struct, but the details of that struct are not made available to the user of the type. This lets us hide the implementation details away from the user of the type and allow them to think about how to use it, rather than how to manage its data. It takes the form of a typedef to a struct pointer and typically ends in &lt;code&gt;Ref&lt;/code&gt;, meaning reference.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Image.h
&lt;/span&gt;&lt;span class=&quot;cp&quot;&gt;#include &amp;lt;stdint.h&amp;gt;
&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;typedef&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;typedef&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;uint32_t&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;

&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageCreate&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fillColor&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageDestroy&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageLoad&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;char&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;filePath&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageGetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageSetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

&lt;span class=&quot;c1&quot;&gt;// Image_Internal.h
&lt;/span&gt;&lt;span class=&quot;cp&quot;&gt;#include &quot;Image.h&quot;
&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixels&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;};&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;typedef&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h2 id=&quot;in-recent-memory&quot;&gt;In Recent Memory&lt;/h2&gt;

&lt;p&gt;Up to here we’ve ignored the topic of &lt;a href=&quot;https://en.wikipedia.org/wiki/Memory_management&quot;&gt;memory management&lt;/a&gt;. In C, data must be placed either on the stack by declaring local variables within a scope, or on the heap using memory allocation functions like &lt;code&gt;malloc()&lt;/code&gt; and &lt;code&gt;free()&lt;/code&gt;. The &lt;code&gt;ImageCreate()&lt;/code&gt; and &lt;code&gt;ImageDestroy()&lt;/code&gt; methods, for example, would look something like this:&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Image.c
&lt;/span&gt;&lt;span class=&quot;cp&quot;&gt;#include &quot;Image.h&quot;
#include &quot;Image_Internal.h&quot;
#include &amp;lt;stdlib.h&amp;gt;
&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ImageCreate&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fillColor&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;malloc&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;sizeof&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;));&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;width&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;height&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pixels&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;malloc&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;sizeof&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pixels&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;width&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fillColor&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ImageDestroy&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;free&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pixels&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;free&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;When the image is created using &lt;code&gt;ImageCreate()&lt;/code&gt;, it will take up memory on the heap until it is freed using &lt;code&gt;ImageDestroy()&lt;/code&gt;. This Create/Destroy mechanism is pretty straightforward. It’s not as easy to use as automatic memory management, but it gets the job done. What about &lt;code&gt;ImageLoad()&lt;/code&gt; though? Does it need to be destroyed? Load/Destroy doesn’t have quite the symmetry of Create/Destroy, but it does need to be done. If it is not destroyed when we’re done with it, the associated memory leaks and is left unavailable for other uses. We must make this clear in documentation in the header.&lt;/p&gt;

&lt;p&gt;If we’re defining a set of objects that will work together, though, we can create a consistent set of names to better self-document what should be destroyed. Just changing the name of &lt;code&gt;ImageLoad()&lt;/code&gt; to &lt;code&gt;ImageCreateByLoading()&lt;/code&gt; allows us to establish a Create/Destroy pattern. So anything you get from a call to a function containing Create must be matched with a call to a Destroy function. Patterns like these assist in knowing what is required without forcing users to comb through the documentation.&lt;/p&gt;

&lt;p&gt;We can use other memory management mechanisms too, like &lt;a href=&quot;https://en.wikipedia.org/wiki/Reference_counting&quot;&gt;Reference Counting&lt;/a&gt;, but that’s a topic for another day.&lt;/p&gt;

&lt;h2 id=&quot;roll-your-own-or-core-foundation&quot;&gt;Roll-Your-Own or Core Foundation&lt;/h2&gt;

&lt;p&gt;We’ve succeeded in creating an image type in C99 that is almost as easy to use as an image class built using an OOP-native language. The ease of use can be made even better, and can even be extended to provide other OOP features like introspection and polymorphism. Container types like sets, lists, and maps are also extremely handy and make using C objects easy. You can either write your own (not as bad as you might think), or use a library. Libraries having these have been implemented by many groups. One of the best is &lt;a href=&quot;https://github.com/opensource-apple/CF&quot;&gt;Core Foundation&lt;/a&gt; by Apple Inc.&lt;/p&gt;

&lt;p&gt;Core Foundation was originally created during the Mac OS 9 to Mac OS X transition and packaged in the Carbon Framework. It has been open-sourced and contains container objects as well as many advanced objects built in much the way described here, using a reference counted memory model. It’s a large library, though, and may be providing more than you need. If you don’t find it perfect to form the basis for your shared app codebase, build your own! For a smooth ride, reinventing the wheel is better than using one that is &lt;a href=&quot;http://www.discovery.com/tv-shows/mythbusters/videos/square-wheels/&quot;&gt;the wrong shape&lt;/a&gt;.&lt;/p&gt;

&lt;h2 id=&quot;bringing-it-all-together&quot;&gt;Bringing it All Together&lt;/h2&gt;

&lt;p&gt;There are 3 files to define the Image opaque type. The header file Image.h contains the opaque type definition and the public functions defined on that type. The private header Image-Internal.h defines the type&amp;#39;s structure and private function interface. The implementation file Image.c defines how the object performs its actions. You can compile Image.c using a variety of tools, and can even distribute the compiled Image object code (Image.o or Image.a) and the public header without the private header for use in other projects. I&amp;#39;ve also provided a simple main method to show how the type is used.&lt;/p&gt;
&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// main.c
&lt;/span&gt;&lt;span class=&quot;cp&quot;&gt;#include &quot;Image.h&quot;
#include &amp;lt;stdio.h&amp;gt;
&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;main&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;()&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageCreate&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;mi&quot;&gt;100&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;100&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mh&quot;&gt;0xFF00FF00&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixel&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageGetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;10&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;10&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;printf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;Pixel (10,10): %i&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;n&quot;&gt;ImageSetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;10&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;10&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mh&quot;&gt;0x00000000&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;pixel&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageGetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;10&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;10&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;printf&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;s&quot;&gt;&quot;Pixel (10,10): %i&quot;&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

    &lt;span class=&quot;n&quot;&gt;ImageDestroy&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Image.h
&lt;/span&gt;&lt;span class=&quot;cp&quot;&gt;#include &amp;lt;stdint.h&amp;gt;
&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;typedef&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;typedef&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;uint32_t&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;

&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageCreate&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fillColor&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageCreateByLoading&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;char&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;filePath&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageDestroy&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageGetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;ImageSetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;

&lt;span class=&quot;c1&quot;&gt;// Image_Internal.h
&lt;/span&gt;&lt;span class=&quot;cp&quot;&gt;#include &quot;Image.h&quot;
&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixels&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;};&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;typedef&lt;/span&gt; &lt;span class=&quot;k&quot;&gt;struct&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre&gt;&lt;code class=&quot;language-c&quot; data-lang=&quot;c&quot;&gt;&lt;span class=&quot;c1&quot;&gt;// Image.c
&lt;/span&gt;&lt;span class=&quot;cp&quot;&gt;#include &quot;Image.h&quot;
#include &quot;Image_Internal.h&quot;
#include &amp;lt;stdlib.h&amp;gt;
&lt;/span&gt;
&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ImageCreate&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fillColor&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;malloc&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;sizeof&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;));&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;width&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;height&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pixels&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;malloc&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;sizeof&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;height&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
        &lt;span class=&quot;k&quot;&gt;for&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;mi&quot;&gt;0&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;&amp;lt;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;width&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;++&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
            &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pixels&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;width&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;fillColor&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
        &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ImageCreateByLoading&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;k&quot;&gt;const&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;char&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;filePath&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;c1&quot;&gt;// TODO: Load image (see later post!)
&lt;/span&gt;    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;nb&quot;&gt;NULL&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ImageDestroy&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;free&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pixels&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;free&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ImageGetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;k&quot;&gt;return&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pixels&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;width&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;];&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;

&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;nf&quot;&gt;ImageSetPixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;ImageRef&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;y&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;,&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;Pixel&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;)&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;{&lt;/span&gt;
    &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;pixels&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;y&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;*&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;image&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;-&amp;gt;&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;width&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;+&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;x&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]&lt;/span&gt; &lt;span class=&quot;o&quot;&gt;=&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;pixel&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;;&lt;/span&gt;
&lt;span class=&quot;p&quot;&gt;}&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h2 id=&quot;relevance-to-android-and-ios&quot;&gt;Relevance to Android and iOS&lt;/h2&gt;

&lt;p&gt;That is object oriented C in a nutshell. There are many ways to go further, adding type systems, polymorphism, introspection, and other features. I hope you enjoy building out beautiful, powerful, portable systems using these techniques.&lt;/p&gt;

&lt;p&gt;So where do we use C in the 21st Century? If you&amp;#39;re writing new code, more likely than not, you&amp;#39;ll find yourself writing code that interacts with mobile or doing mobile application development directly.&lt;/p&gt;

&lt;p&gt;When planning a mobile application that runs on both iOS and Android devices, the development options fall into 3 groups: 1. cross-platform frameworks like Xamarin, 2. native development with two separate codebases, and 3. front-end development for each platform with a shared back-end codebase. The best choice depends heavily on the application being built.&lt;/p&gt;

&lt;p&gt;When your app requirements match best with option #3, a partially shared codebase, a language and tools that generate binaries on both platforms is required. Since Java, the Android favorite, doesn&amp;#39;t run on iOS, and Swift, the Apple favorite, doesn&amp;#39;t run on Android, we have to find something that does. It is possible to tie into code written in C and C++ on Android by making use of the &lt;a href=&quot;https://developer.android.com/ndk/index.html&quot;&gt;Native Development Kit&lt;/a&gt; and on iOS applications written in Swift with the &lt;a href=&quot;https://developer.apple.com/library/ios/documentation/Swift/Conceptual/BuildingCocoaApps/InteractingWithCAPIs.html#//apple_ref/doc/uid/TP40014216-CH8-ID17&quot;&gt;Swift Foreign Function Interface&lt;/a&gt;. This allows developers, by enduring significant pain, to use libraries that run on both platforms.&lt;/p&gt;

&lt;p&gt;Though the Swift FFI supports C++, it does so rather poorly. &lt;a href=&quot;https://github.com/apple/swift-evolution/tree/b55ce1513f1eef80fb780759326d8efb62cec04d&quot;&gt;Swift Programming Language Evolution&lt;/a&gt; states “C++ itself is a very complex language, and providing good interoperability with C++ is a significant undertaking that is out of scope for Swift 3.0.” Current wisdom advocates &lt;a href=&quot;https://en.wikipedia.org/wiki/Wrapper_library&quot;&gt;wrapping&lt;/a&gt; C++ in C or Objective-C, then using the Swift FFI to bring that in. Building new interoperable code with iOS and Android with poor FFI support and wrapping makes C++ a tenuous proposition.&lt;/p&gt;

&lt;p&gt;Other options such as &lt;a href=&quot;http://j2objc.org/&quot;&gt;Google’s j2objc&lt;/a&gt; exist, but usually require many tradeoffs in code structure. Using these techniques to build opaque types in native C keeps writing new shared mobile codebases from becoming contorted pipe dream.&lt;/p&gt;
</description>
        <pubDate>Fri, 03 Jun 2016 00:00:00 -0600</pubDate>
        <link>http://www.pixio.com/blog/2016-06-03/c-in-the-21st-century/</link>
        <guid isPermaLink="true">http://www.pixio.com/blog/2016-06-03/c-in-the-21st-century/</guid>
        
        <category>c99 opaque types</category>
        
        
        <category>tools</category>
        
      </item>
    
      <item>
        <title>Make MBaaS Great Again!</title>
        <description>&lt;p&gt;It&amp;#39;s Google IO time again and one of the biggest announcements from the keynote was the announcement of &lt;a href=&quot;https://firebase.google.com/&quot;&gt;Firebase&lt;/a&gt; expanding to a full mobile platform. Firebase was known mostly as a competitor to Facebook&amp;#39;s &lt;a href=&quot;https://parse.com/&quot;&gt;Parse&lt;/a&gt; service and for their realtime databases. With Facebook sunsetting Parse, Firebase is quickly becoming the go-to &lt;a href=&quot;https://en.wikipedia.org/wiki/Mobile_backend_as_a_service&quot;&gt;MBaaS (Mobile Backend as a Service)&lt;/a&gt; provider for many mobile developers.&lt;/p&gt;

&lt;h2 id=&quot;more-powerful-more-complete&quot;&gt;More Powerful, More Complete&lt;/h2&gt;

&lt;p&gt;The new Firebase Storage provides reliable storage backed by the existing Google Cloud Storage. Additionally, the integrations with the Firebase Authentication tools allow tweaking the permissions of files. Firebase users have been forced to implement their own storage solutions using Amazon S3, Google Cloud Storage, or (worst of all) storing a Base64 string in their realtime database. No more of that nonsense!&lt;/p&gt;

&lt;p&gt;Google Cloud Messaging is being rebranded as Firebase Cloud Messaging and it includes all the cloud messaging functionality of which you are used to along with Firebase&amp;#39;s SDKs sprinkled on top. The SDK is quite powerful and helps reduce the amount of boilerplate code, especially in iOS. In iOS, the Firebase SDK employs &lt;a href=&quot;http://nshipster.com/method-swizzling/&quot;&gt;method swizzling&lt;/a&gt; to automatically write a default implementation for methods that you are required to implement.&lt;/p&gt;

&lt;h2 id=&quot;show-me-the-new-stuff&quot;&gt;Show Me The New Stuff&lt;/h2&gt;

&lt;p&gt;There is a lot of great new functionality in Firebase and much of it consists of existing Google services that have been tweaked to better focus on mobile development. Analytics, GCM, Cloud Test Lab, AdWords, and AdMob are now part of the unified Firebase platform and the integration into Firebase allows them to work together easily.&lt;/p&gt;

&lt;p&gt;Remote Config makes it incredibly easy to update configuration variables on the fly. It takes care of caching the results retrieved from the server and setting default values. Being part of Firebase allows targetted updates of configurations. For example, you could do a slow rollout of a new feature to users and disable that functionality if there&amp;#39;s an issue. This could easily be employed to perform A/B tests.&lt;/p&gt;

&lt;p&gt;Dynamic Links are new to Firebase and add incredible functionality. Dynamic Links open to different content based on which device you are on. If the user does not have the native app installed, they will be sent to their respective app store from which the app can be downloaded. A really powerful feature of Dynamic Links is that they are able to persist through the app store. This allows you to track the efficacy of new user acquisition as well as provide the best possible onboarding experience for your users.&lt;/p&gt;

&lt;h2 id=&quot;that-39-s-cool-but-why-do-i-care&quot;&gt;That&amp;#39;s cool, but why do I care?&lt;/h2&gt;

&lt;p&gt;Firebase remains a powerful &lt;a href=&quot;https://en.wikipedia.org/wiki/Mobile_backend_as_a_service&quot;&gt;MBaaS&lt;/a&gt; and much of the added functionality helps to make it even better. However, a huge focus of the new and improved platform is analytics. Most of the tools provided by the new Firebase are tightly integrated with the analytics suite. This integration allow you to understand your target users as well as their interactions with your application in it&amp;#39;s entirety. As developers, it&amp;#39;s easy for us to think that we are always right (and our users are wrong) and that&amp;#39;s a dangerous thought. It&amp;#39;s important to understand our users and then react and respond to them. Ultimately, this leads to a better quality application.&lt;/p&gt;

&lt;h2 id=&quot;i-see-dead-people&quot;&gt;I See Dead People&lt;/h2&gt;

&lt;p&gt;I&amp;#39;m scared. I&amp;#39;m really scared. What happens if Firebase goes away in a year? Google doesn&amp;#39;t have a great &lt;a href=&quot;https://en.wikipedia.org/wiki/List_of_Google_products#Discontinued_products_and_services&quot;&gt;track record&lt;/a&gt;. Parse had over 500,000 users and Facebook still killed the service. Why won&amp;#39;t Firebase disappear just like Parse?&lt;/p&gt;

&lt;p&gt;None of us can predict the future of how Firebase will fare and by using the services, you are placing your trust in a 3rd party that you have no control over. With Firebase approaching the numbers that Parse was seeing, it&amp;#39;s hard not to draw comparisons. It&amp;#39;s up to you do to the cost-benefit analysis of the possibility that Firebase gets shut down.&lt;/p&gt;

&lt;p&gt;In order to mitigate the possiblity that Firebase disappears, it&amp;#39;s important to understand the system at a high level. If you have no idea how a particular system that you are using works and you&amp;#39;re locked in, the pain of migrating away all the more frustrating. Architecting your client-side application in such a way that the backend infrastructure implementation details will help you mitigate any issues that may arise in the future.&lt;/p&gt;

&lt;h2 id=&quot;easily-breeze-ily-firebase-ily&quot;&gt;Easily, Breeze-ily, Firebase-ily&lt;/h2&gt;

&lt;p&gt;The great thing about the new Firebase Platform is the modularity. It&amp;#39;s not an all or nothing system. You can pick and choose components and still use external services such as Twitter&amp;#39;s &lt;a href=&quot;https://fabric.io/&quot;&gt;Fabric mobile platform&lt;/a&gt; or &lt;a href=&quot;https://developer.yahoo.com/analytics/&quot;&gt;Flurry Analytics&lt;/a&gt;. Employing tools provided by Firebase allows you to really quickly build a full application without a backend and understand your users.&lt;/p&gt;

&lt;p&gt;Firebase (and other tools and platforms in the ecosystem) are important tools for your application. They provide vast functionality to help your application succeed in a large market. They allow you to focus on creating the application, and not the support structure around that application. Whether or not you use any of Firebase&amp;#39;s tools, it&amp;#39;s valuable to understand the problems they solve and keep those in mind when building your own applications.&lt;/p&gt;
</description>
        <pubDate>Fri, 20 May 2016 00:00:00 -0600</pubDate>
        <link>http://www.pixio.com/blog/2016-05-20/make-mbaas-great-again/</link>
        <guid isPermaLink="true">http://www.pixio.com/blog/2016-05-20/make-mbaas-great-again/</guid>
        
        <category>firebase</category>
        
        
        <category>tools</category>
        
      </item>
    
      <item>
        <title>The University of Utah Senior Project Fair</title>
        <description>&lt;p&gt;Recently, the University of Utah held its annual fair to show off the year-long projects created by the Computer Science department&amp;#39;s graduating seniors.&lt;/p&gt;

&lt;h1 id=&quot;we-were-invited&quot;&gt;We were invited&lt;/h1&gt;

&lt;p&gt;I swear! Don&amp;#39;t get me wrong, we discussed possibly renting uniforms that bore a striking resemblance to some of the University of Utah employees you&amp;#39;ll see around campus. Heck, there were even talks about who would fit under a food cart with a white blanket draped over it. In the end, the Computer Science Department at Utah asked one of our Founders, Matt Stoker (who also teaches the mobile development class), to judge so we all tagged along.&lt;/p&gt;

&lt;h1 id=&quot;we-were-impressed&quot;&gt;We were impressed&lt;/h1&gt;

&lt;p&gt;Judging gave us a unique opportunity to interact with the students that worked on these projects. We were given a run down on their software&amp;#39;s functionality and the technology/effort that went into making them. Here are some of our favorites:&lt;/p&gt;

&lt;h2 id=&quot;principia&quot;&gt;&lt;a href=&quot;http://principia.cc/&quot;&gt;Principia&lt;/a&gt;&lt;/h2&gt;

&lt;p&gt;Principia is a physics playground. It is intended to help students learn physics and finish their homework. You can enter in the constraints of a homework problem, simulate it, and check to make sure your calculations weren&amp;#39;t off.&lt;/p&gt;

&lt;p&gt;We were impressed with the detail of the physics simulations. Also, we thought that their app was very thought out, and polished enough to be used in production.&lt;/p&gt;

&lt;p&gt;My favorite part, however, was this simulation:&lt;/p&gt;

&lt;p&gt;&lt;img src=&quot;../../../img/posts/internal/the_joker_got_away.png&quot; alt=&quot;alt text&quot; title=&quot;Batmobile lost its wheel&quot;&gt;&lt;/p&gt;

&lt;p&gt;If the batmobile did in fact lose a wheel, would the joker be able to get away?&lt;/p&gt;

&lt;p&gt;You can see this project &lt;a href=&quot;http://principia.cc/&quot;&gt;here&lt;/a&gt;&lt;/p&gt;

&lt;h2 id=&quot;schoolbloc&quot;&gt;&lt;a href=&quot;http://schoolbloc.co/&quot;&gt;SchoolBloc&lt;/a&gt;&lt;/h2&gt;

&lt;p&gt;Working with a local charter school, SchoolBloc set out to create a system that would help schools figure out an optimal schedule for each one of their enrolled students.&lt;/p&gt;

&lt;p&gt;We were impressed because we thought this team took the correct approach in using a constraint solver. We also appreciated the fact that this team was working with a local school to solve an immediate issue.&lt;/p&gt;

&lt;p&gt;You can see this project &lt;a href=&quot;http://schoolbloc.co/&quot;&gt;here&lt;/a&gt;&lt;/p&gt;

&lt;h2 id=&quot;played&quot;&gt;&lt;a href=&quot;http://www.playedsmart.com/&quot;&gt;PlayED&lt;/a&gt;&lt;/h2&gt;

&lt;p&gt;We at Pixio appreciate gamification, and PlayED is aiming to do just that. PlayED is a platform for teachers to give elementary-aged students &amp;quot;assignments&amp;quot; (and by assignments I mean math and english focused games to play) and track their progress and scores through an analytics dashboard.&lt;/p&gt;

&lt;p&gt;We were mainly impressed with the amount that the PlayED team was able to get done. They were able to create 3 example games in WebGL, as well as an intuitive dashboard application for the teachers to access their students&amp;#39; data.&lt;/p&gt;

&lt;p&gt;You can see this project &lt;a href=&quot;http://www.playedsmart.com/&quot;&gt;here&lt;/a&gt;&lt;/p&gt;

&lt;h1 id=&quot;the-competition&quot;&gt;The competition&lt;/h1&gt;

&lt;p&gt;In the end, SchoolBloc came in third, Principia came in second, and AirU (an app that gathers and displays air quality across the United States) won the competition.&lt;/p&gt;

&lt;h1 id=&quot;in-conclusion&quot;&gt;In conclusion&lt;/h1&gt;

&lt;p&gt;We all had a lot of fun meeting a bunch of really smart people and talking to them about what cool things they were able to accomplish over the past few months. We love being able to be involved in the community, and look forward to events like this.&lt;/p&gt;

&lt;p&gt;One sentence summary: We came, we judged, we got free pizza.&lt;/p&gt;
</description>
        <pubDate>Fri, 13 May 2016 00:00:00 -0600</pubDate>
        <link>http://www.pixio.com/blog/2016-05-13/the-university-of-utah-senior-project-fair/</link>
        <guid isPermaLink="true">http://www.pixio.com/blog/2016-05-13/the-university-of-utah-senior-project-fair/</guid>
        
        <category>university of utah</category>
        
        <category>local</category>
        
        <category>outreach</category>
        
        
        <category>community</category>
        
      </item>
    
  </channel>
</rss>