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<!DOCTYPE html>
<html>
<head>
<title>Overcoming Our Obsession With Stringly-Typed Ruby</title>
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<body><div id="contents">
<section class='TITLE'>
<h1>Overcoming Our Obsession With Stringly-Typed Ruby</h1>
<h2>Dave Copeland · @davetron5000</h2>
<h3>http://www.naildrivin5.com · http://technology.stitchfix.com</h3>
</section>
<section class='IMAGE'>
<img src='images/cover.png'>
</section>
<section class='IMAGE'>
<img src='images/dccar2.jpg'>
</section>
<section class='TITLE'>
<h1>Overcoming Our Obsession With <br><i>Stringly-Typed</i> Ruby</h1>
</section>
<section class='SECTION'>
<h1>Stringly-Typed</h1>
<h2>From @codinghorror's “New Programmer Jargon”</h2>
<h3><a href="http://blog.codinghorror.com/new-programming-jargon/">http://blog.codinghorror.com/new-programming-jargon/</a></h3>
</section>
<section class='QUOTE'>
<h1>A riff on “strongly typed”. </h1>
<h2>Used to describe an implementation that needlessly relies on strings when programmer & refactor-friendly options are available.</h2>
</section>
<section class='SECTION'>
<h1>A tale of two zip codes</h1>
<h2>U.S. postal codes</h2>
<h3>aka "Zip Codes"</h3>
</section>
<section class='BULLETS'>
<h1>Zip Codes</h1>
<ul>
<li>Five Digits, e.g. 90210</li>
<li>Map to an area of the U.S.</li>
</ul>
</section>
<section class='IMAGE'>
<img src='images/zipcode_map.png'>
</section>
<section class='BULLETS'>
<h1>Simple App</h1>
<ul>
<li>Store addresses in a DB</li>
<li>Send letters to an address</li>
</ul>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='2,3,4'><span class='line line-1 ' >module ThirdPartyMailingService</span>
<div class='lines-callout'><span class='line line-2 line-callout' > def self.find_letter(letter_id)</span>
<span class='line line-3 line-callout' > # ...</span>
<span class='line line-4 line-callout' > end</span>
</div><span class='line line-5 ' ></span>
<span class='line line-6 ' > class Letter</span>
<span class='line line-7 ' > def mail!(street,city,state,zip_code)</span>
<span class='line line-8 ' > # ...</span>
<span class='line line-9 ' > end</span>
<span class='line line-10 ' > end</span>
<span class='line line-11 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='6,7,8,9,10'><span class='line line-1 ' >module ThirdPartyMailingService</span>
<span class='line line-2 ' > def self.find_letter(letter_id)</span>
<span class='line line-3 ' > # ...</span>
<span class='line line-4 ' > end</span>
<span class='line line-5 ' ></span>
<div class='lines-callout'><span class='line line-6 line-callout' > class Letter</span>
<span class='line line-7 line-callout' > def mail!(street,city,state,zip_code)</span>
<span class='line line-8 line-callout' > # ...</span>
<span class='line line-9 line-callout' > end</span>
<span class='line line-10 line-callout' > end</span>
</div><span class='line line-11 ' >end</span>
<span class='line line-12 ' ></span></code></pre>
</section>
<section class='CODE'>
<pre><code class='sql' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >create table addresses(</span>
<span class='line line-2 ' > id int not null,</span>
<span class='line line-3 ' > street varchar(256) not null,</span>
<span class='line line-4 ' > city varchar(256) not null,</span>
<span class='line line-5 ' > state char(2) not null,</span>
<span class='line line-6 ' > zip_code char(5) not null</span>
<span class='line line-7 ' >)</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='5,6'><span class='line line-1 ' >class AddressReader</span>
<span class='line line-2 ' > def read_new_address</span>
<span class='line line-3 ' > puts "Enter your address"</span>
<span class='line line-4 ' ></span>
<div class='lines-callout'><span class='line line-5 line-callout' > puts "street?"</span>
<span class='line line-6 line-callout' > street = gets</span>
</div><span class='line line-7 ' ></span>
<span class='line line-8 ' > puts "city?"</span>
<span class='line line-9 ' > city = gets</span>
<span class='line line-10 ' ></span>
<span class='line line-11 ' > puts "state?"</span>
<span class='line line-12 ' > state = gets</span>
<span class='line line-13 ' ></span>
<span class='line line-14 ' > puts "zip code?"</span>
<span class='line line-15 ' > zip_code = gets</span>
<span class='line line-16 ' ></span>
<span class='line line-17 ' > id = $database.insert_into(:addresses,</span>
<span class='line line-18 ' > street: street,</span>
<span class='line line-19 ' > city: city,</span>
<span class='line line-20 ' > state: state,</span>
<span class='line line-21 ' > zip_code: zip_code)</span>
<span class='line line-22 ' > </span>
<span class='line line-23 ' > puts "Created address #{id}"</span>
<span class='line line-24 ' > end</span>
<span class='line line-25 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='17,18,19,20,21'><span class='line line-1 ' >class AddressReader</span>
<span class='line line-2 ' > def read_new_address</span>
<span class='line line-3 ' > puts "Enter your address"</span>
<span class='line line-4 ' ></span>
<span class='line line-5 ' > puts "street?"</span>
<span class='line line-6 ' > street = gets</span>
<span class='line line-7 ' ></span>
<span class='line line-8 ' > puts "city?"</span>
<span class='line line-9 ' > city = gets</span>
<span class='line line-10 ' ></span>
<span class='line line-11 ' > puts "state?"</span>
<span class='line line-12 ' > state = gets</span>
<span class='line line-13 ' ></span>
<span class='line line-14 ' > puts "zip code?"</span>
<span class='line line-15 ' > zip_code = gets</span>
<span class='line line-16 ' ></span>
<div class='lines-callout'><span class='line line-17 line-callout' > id = $database.insert_into(:addresses,</span>
<span class='line line-18 line-callout' > street: street,</span>
<span class='line line-19 line-callout' > city: city,</span>
<span class='line line-20 line-callout' > state: state,</span>
<span class='line line-21 line-callout' > zip_code: zip_code)</span>
</div><span class='line line-22 ' > </span>
<span class='line line-23 ' > puts "Created address #{id}"</span>
<span class='line line-24 ' > end</span>
<span class='line line-25 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='3'><span class='line line-1 ' >class LetterSender</span>
<span class='line line-2 ' > def send_letter(letter_id,address_hash)</span>
<div class='lines-callout'><span class='line line-3 line-callout' > letter = ThirdPartyMailingService.find_letter(letter_id)</span>
</div><span class='line line-4 ' > letter.mail!(address_hash[:street],</span>
<span class='line line-5 ' > address_hash[:city],</span>
<span class='line line-6 ' > address_hash[:state],</span>
<span class='line line-7 ' > address_hash[:zip_code])</span>
<span class='line line-8 ' > end</span>
<span class='line line-9 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='4,5,6,7'><span class='line line-1 ' >class LetterSender</span>
<span class='line line-2 ' > def send_letter(letter_id,address_hash)</span>
<span class='line line-3 ' > letter = ThirdPartyMailingService.find_letter(letter_id)</span>
<div class='lines-callout'><span class='line line-4 line-callout' > letter.mail!(address_hash[:street],</span>
<span class='line line-5 line-callout' > address_hash[:city],</span>
<span class='line line-6 line-callout' > address_hash[:state],</span>
<span class='line line-7 line-callout' > address_hash[:zip_code])</span>
</div><span class='line line-8 ' > end</span>
<span class='line line-9 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='3,4'><span class='line line-1 ' >class Mailer</span>
<span class='line line-2 ' > def send_letter(address_id,letter_id)</span>
<div class='lines-callout'><span class='line line-3 line-callout' > address_hash = $database.select_from(:addresses,</span>
<span class='line line-4 line-callout' > :id => address_id)</span>
</div><span class='line line-5 ' > LetterSender.new.send_letter(letter_id, to: address_hash)</span>
<span class='line line-6 ' > puts "Letter ##{letter_id} sent to"</span>
<span class='line line-7 ' > puts address_hash[:street]</span>
<span class='line line-8 ' > puts "#{address_hash[:city], #{address_hash[:state]}, #{address_hash[:zip_code]}"</span>
<span class='line line-9 ' > end</span>
<span class='line line-10 ' >end</span>
<span class='line line-11 ' ></span>
<span class='line line-12 ' >Mailer.new.send_letter(ARGV[0].to_i, ARGV[1].to_i)</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='5'><span class='line line-1 ' >class Mailer</span>
<span class='line line-2 ' > def send_letter(address_id,letter_id)</span>
<span class='line line-3 ' > address_hash = $database.select_from(:addresses,</span>
<span class='line line-4 ' > :id => address_id)</span>
<div class='lines-callout'><span class='line line-5 line-callout' > LetterSender.new.send_letter(letter_id, to: address_hash)</span>
</div><span class='line line-6 ' > puts "Letter ##{letter_id} sent to"</span>
<span class='line line-7 ' > puts address_hash[:street]</span>
<span class='line line-8 ' > puts "#{address_hash[:city], #{address_hash[:state]}, #{address_hash[:zip_code]}"</span>
<span class='line line-9 ' > end</span>
<span class='line line-10 ' >end</span>
<span class='line line-11 ' ></span>
<span class='line line-12 ' >Mailer.new.send_letter(ARGV[0].to_i, ARGV[1].to_i)</span></code></pre>
</section>
<section class='COMMANDLINE'>
<pre><code class='no-highlight'><span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> ./store_address.rb</span>
<span class='cli-element cli-result'><span class='cli-line'>street?</span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> 45 S. Fair Oaks Ave</span>
<span class='cli-element cli-result'><span class='cli-line'>city?</span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> Beverley Hills</span>
<span class='cli-element cli-result'><span class='cli-line'>state?</span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> CA</span>
<span class='cli-element cli-result'><span class='cli-line'>zip?</span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> 90210</span>
<span class='cli-element cli-result'><span class='cli-line'>You created address 42</span></span>
</code></pre>
</section>
<section class='COMMANDLINE'>
<pre><code class='no-highlight'><span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> ./send_letter.rb 42 12</span>
<span class='cli-element cli-result'><span class='cli-line'>Letter #12 sent to</span>
<span class='cli-line'>45 S. Fair Oaks Ave</span>
<span class='cli-line'>Beverley Hills, CA 90210</span></span>
</code></pre>
</section>
<section class='COMMANDLINE'>
<pre><code class='no-highlight'><span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> ./store_address.rb</span>
<span class='cli-element cli-result'><span class='cli-line'>street?</span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> 1675 E Altadena Dr</span>
<span class='cli-element cli-result'><span class='cli-line'>city?</span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> Altadena</span>
<span class='cli-element cli-result'><span class='cli-line'>state?</span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> CA</span>
<span class='cli-element cli-result'><span class='cli-line'>zip?</span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> WALSH</span>
<span class='cli-element cli-result'><span class='cli-line'>You created address 43</span></span>
</code></pre>
</section>
<section class='COMMANDLINE'>
<pre><code class='no-highlight'><span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> ./send_letter.rb 43 12</span>
<span class='cli-element cli-result'><span class='cli-line'>Letter #12 sent to</span>
<span class='cli-line'>1675 E Altadena Dr</span>
<span class='cli-line'>Altadena, CA WALSH</span></span>
</code></pre>
</section>
<section class='NORMAL'>
<h1>Oops</h1>
</section>
<section class='NORMAL'>
<h1>Must be a problem reading input!</h1>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='3,4,5'><span class='line line-1 ' >zip_code = gets</span>
<span class='line line-2 ' ></span>
<div class='lines-callout'><span class='line line-3 line-callout' >unless zip_code =~ /^[0-9]{5}$/</span>
<span class='line line-4 line-callout' > raise "not a zip code" </span>
<span class='line line-5 line-callout' >end</span></div></code></pre>
</section>
<section class='CODE'>
<pre><code class='sql' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >INSERT INTO</span>
<span class='line line-2 ' > addresses(street,city,state,zip)</span>
<span class='line line-3 ' >VALUES</span>
<span class='line line-4 ' > ('1675 E Altadena Dr'</span>
<span class='line line-5 ' > 'Altadena',</span>
<span class='line line-6 ' > 'CA',</span>
<span class='line line-7 ' > 'WALSH')</span></code></pre>
</section>
<section class='NORMAL'>
<h1>Oh! Oh!</h1>
<h2>A problem in our database design!</h2>
</section>
<section class='CODE'>
<pre><code class='sql,' data-strikeouts='' data-callout-lines='5,6,7'><span class='line line-1 ' >ALTER TABLE</span>
<span class='line line-2 ' > addresses</span>
<span class='line line-3 ' >ADD CONSTRAINT</span>
<span class='line line-4 ' > looks_like_a_zipcode</span>
<div class='lines-callout'><span class='line line-5 line-callout' >CHECK (</span>
<span class='line line-6 line-callout' > (zip ~* '^[0-9]{5}$')</span>
<span class='line line-7 line-callout' >)</span></div></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >LetterSender.new.send_letter(letter_id,</span>
<span class='line line-2 ' > street: '1675 E Altadena Dr'</span>
<span class='line line-3 ' > city: 'Altadena',</span>
<span class='line line-4 ' > state: 'CA',</span>
<span class='line line-5 ' > zip_code: 'WALSH')</span></code></pre>
</section>
<section class='IMAGE'>
<img src='images/buzz.png'>
</section>
<section class='SECTION'>
<h1>This is not how to build a maintainable system</h1>
</section>
<section class='IMAGE'>
<img src='images/loose_boundaries.png'>
</section>
<section class='SECTION'>
<h1>Boundaries</h1>
</section>
<section class='NORMAL'>
<h1>What's coming and what's going</h1>
</section>
<section class='IMAGE'>
<img src='images/method.png'>
</section>
<section class='IMAGE'>
<img src='images/strings_and_hashes.png'>
</section>
<section class='SECTION'>
<h1>Data Types</h1>
</section>
<section class='BULLETS'>
<h1>Data Types</h1>
<ul>
<li>Possible Values</li>
<li>Allowed Operations</li>
<li>What they mean</li>
</ul>
</section>
<section class='FREEFORM'>
<table>
<thead>
<th></th>
<th>String</th>
<th>Zip Code</th>
</thead>
<tbody>
<tr>
<th>Possible values</th>
<td>Anything</td>
<td>Five Digits</td>
</tr>
<tr>
<th>Operations</th>
<td>A ton</td>
<td>Pretty much none</td>
</tr>
<tr>
<th>What They Mean</th>
<td>Anything</td>
<td>Location in the U.S.</td>
</tr>
</tbody>
</table>
</section>
<section class='IMAGE'>
<img src='images/strong_boundaries.png'>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >class ZipCode</span>
<span class='line line-2 ' > def initialize(string)</span>
<span class='line line-3 ' > @raw_zipcode = string</span>
<span class='line line-4 ' > end</span>
<span class='line line-5 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >class ZipCode</span>
<span class='line line-2 ' > def initialize(string)</span>
<span class='line line-3 ' > unless string =~ /^\d\d\d\d\d$/</span>
<span class='line line-4 ' > raise 'invalid zipcode' </span>
<span class='line line-5 ' > end</span>
<span class='line line-6 ' > @raw_zipcode = string</span>
<span class='line line-7 ' > end</span>
<span class='line line-8 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >zip1 = ZipCode.new("90210")</span>
<span class='line line-2 ' ></span>
<span class='line line-3 ' >zip2 = ZipCode.new("WALSH")</span>
<span class='line line-4 ' ># => boom</span>
<span class='line line-5 ' ># zip2 never gets assigned</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >class ZipCode</span>
<span class='line line-2 ' > def raw_zipcode</span>
<span class='line line-3 ' > @raw_zipcode</span>
<span class='line line-4 ' > end</span>
<span class='line line-5 ' >end</span></code></pre>
</section>
<section class='IMAGE'>
<img src='images/strong_boundaries.png'>
</section>
<section class='BULLETS'>
<h1>Design Activity</h1>
<ul>
<li>What problem am I solving?</li>
<li>Push code around to solve it</li>
<li>Define boundaries using data types</li>
</ul>
</section>
<section class='SECTION'>
<h1>How do we publicize these boundaries?</h1>
</section>
<section class='BULLETS'>
<h1>Conventions</h1>
<ul>
<li>Underscorize the classname, e.g. <code>zip_code</code></li>
<li>Suffix with underscorized, e.g. <code>sender_zip_code</code></li>
<li>Document public methods</li>
</ul>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >class FooBar</span>
<span class='line line-2 ' ></span>
<span class='line line-3 ' > # zip_code:: instance of ZipCode to geolocate</span>
<span class='line line-4 ' > def geolocate(zip_code)</span>
<span class='line line-5 ' > end</span>
<span class='line line-6 ' ></span>
<span class='line line-7 ' > # Returns a ZipCode nearest the given lat and long</span>
<span class='line line-8 ' > def nearest_zip_code(lat,long)</span>
<span class='line line-9 ' > end</span>
<span class='line line-10 ' ></span>
<span class='line line-11 ' >private</span>
<span class='line line-12 ' ></span>
<span class='line line-13 ' > def center_point(zip_code)</span>
<span class='line line-14 ' > end</span>
<span class='line line-15 ' >end</span></code></pre>
</section>
<section class='SECTION'>
<h1>Can we enforce this?</h1>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='3'><span class='line line-1 ' >class FooBar</span>
<span class='line line-2 ' > def geolocate(zip_code)</span>
<div class='lines-callout'><span class='line line-3 line-callout' > unless zip_code.is_a?(ZipCode)</span>
</div><span class='line line-4 ' > raise ArgumentError, "must be a ZipCode"</span>
<span class='line line-5 ' > end</span>
<span class='line line-6 ' > # ...</span>
<span class='line line-7 ' > end</span>
<span class='line line-8 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='3'><span class='line line-1 ' >class FooBar</span>
<span class='line line-2 ' > def geolocate(zip_code)</span>
<div class='lines-callout'><span class='line line-3 line-callout' > unless zip_code.instance_of?(ZipCode)</span>
</div><span class='line line-4 ' > raise ArgumentError, "must be a ZipCode"</span>
<span class='line line-5 ' > end</span>
<span class='line line-6 ' > # ...</span>
<span class='line line-7 ' > end</span>
<span class='line line-8 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='3'><span class='line line-1 ' >class FooBar</span>
<span class='line line-2 ' > def geolocate(zip_code)</span>
<div class='lines-callout'><span class='line line-3 line-callout' > unless zip_code.respond_to?(:raw_zipcode)</span>
</div><span class='line line-4 ' > raise ArgumentError, "must implement #raw_zipcode"</span>
<span class='line line-5 ' > end</span>
<span class='line line-6 ' > # ...</span>
<span class='line line-7 ' > end</span>
<span class='line line-8 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='4'><span class='line line-1 ' >class FooBarTest</span>
<span class='line line-2 ' > def test_that_we_get_the_right_data_type</span>
<span class='line line-3 ' > result = foo_bar.nearest_zip_code(lat,long)</span>
<div class='lines-callout'><span class='line line-4 line-callout' > assert result.is_a?(ZipCode), </span>
</div><span class='line line-5 ' > "Got a #{result.class} instead :("</span>
<span class='line line-6 ' > end</span>
<span class='line line-7 ' >end</span></code></pre>
</section>
<section class='SECTION'>
<h1><strong>Should</strong> we?</h1>
</section>
<section class='IMAGE'>
<img src='images/types_everywhere.png'>
</section>
<section class='IMAGE'>
<img src='images/scala-logo.png'>
</section>
<section class='BULLETS'>
<h1>Two Times You Might</h1>
<ul>
<li>Risk</li>
<li>Big Refactor</li>
</ul>
</section>
<section class='BULLETS'>
<h1>Risk</h1>
<ul>
<li>How often do we expect a bad type?</li>
<li>What happens if a one does?</li>
</ul>
</section>
<section class='BULLETS'>
<h1>Big Refactor (w/compiler)</h1>
<ul>
<li>Change core types as needed</li>
<li>Compile</li>
<li>Fix the errors</li>
</ul>
</section>
<section class='BULLETS'>
<h1>Big Refactor (no compiler)</h1>
<ul>
<li>Change core types as needed</li>
<li>Add explicit type checks</li>
<li>Run tests</li>
<li>Fix the errors</li>
<li>Remove explicit type checks</li>
</ul>
</section>
<section class='BULLETS'>
<h1>When The World Wants/Has Strings</h1>
<ul>
<li>Protocols - Data Type → String</li>
<li>Wrappers - String → Data Type</li>
</ul>
</section>
<section class='SECTION'>
<h1>Protocols</h1>
<h2><a href="http://www.confidentruby.com">www.confidentruby.com</a></h2>
<h3>Chapter 4.2</h3>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >class ZipCode</span>
<span class='line line-2 ' > def initialize(string)</span>
<span class='line line-3 ' > unless string =~ /^\d\d\d\d\d$/</span>
<span class='line line-4 ' > raise 'invalid zipcode' </span>
<span class='line line-5 ' > end</span>
<span class='line line-6 ' > @raw_zipcode = string</span>
<span class='line line-7 ' > end</span>
<span class='line line-8 ' ></span>
<span class='line line-9 ' > def raw_zipcode</span>
<span class='line line-10 ' > @raw_zipcode</span>
<span class='line line-11 ' > end</span>
<span class='line line-12 ' >end</span></code></pre>
</section>
<section class='COMMANDLINE'>
<pre><code class='no-highlight'><span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> zip = ZipCode.new("90210")</span>
<span class='cli-element cli-result'><span class='cli-line'><ZipCode:0x007fb02d8b0968 @raw_zipcode="90210"></span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> puts zip</span>
<span class='cli-element cli-result'><span class='cli-line'><ZipCode:0x007fb02d8b0968></span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> puts "The zip is #{zip}"</span>
<span class='cli-element cli-result'><span class='cli-line'>The zip is <ZipCode:0x007fb02d8b0968></span></span>
</code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >class ZipCode</span>
<span class='line line-2 ' > alias to_s raw_zipcode</span>
<span class='line line-3 ' >end</span></code></pre>
</section>
<section class='COMMANDLINE'>
<pre><code class='no-highlight'><span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> puts "The zip is #{zip}"</span>
<span class='cli-element cli-result'><span class='cli-line'>The zip is 90210</span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> puts "The zip is " + zip</span>
<span class='cli-element cli-result'><span class='cli-line'>TypeError: no implicit conversion of ZipCode into String</span>
<span class='cli-line'> from (irb):12:in `+'</span>
<span class='cli-line'> from (irb):12</span>
<span class='cli-line'> from /Users/davec/.rvm/rubies/ruby-2.1.0/bin/irb:11:in `<main>'</span></span>
</code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >class ZipCode</span>
<span class='line line-2 ' > alias to_str raw_zipcode</span>
<span class='line line-3 ' >end</span></code></pre>
</section>
<section class='COMMANDLINE'>
<pre><code class='no-highlight'><span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> puts "The zip is " + zip</span>
<span class='cli-element cli-result'><span class='cli-line'>The zip is 90210</span></span>
</code></pre>
</section>
<section class='CODE'>
<pre><code class='html' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' ><dt>ZipCode</dt></span>
<span class='line line-2 ' ><dd><%= zip_code %></dd></span></code></pre>
</section>
<section class='BULLETS'>
<h1>Non-String Goodies, too</h1>
<ul>
<li><code>to_a</code></li>
<li><code>to_int</code></li>
<li><code>to_h</code></li>
</ul>
</section>
<section class='SECTION'>
<h1>Wrappers</h1>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >class Mailer</span>
<span class='line line-2 ' > def send_letter(address_id,letter_id)</span>
<span class='line line-3 ' > address_hash = $database.select_from(:addresses,</span>
<span class='line line-4 ' > :id => address_id)</span>
<span class='line line-5 ' ></span>
<span class='line line-6 ' > LetterSender.new.send_letter(letter_id, to: address_hash)</span>
<span class='line line-7 ' > end</span>
<span class='line line-8 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby,' data-strikeouts='' data-callout-lines='3'><span class='line line-1 ' >class WrappingDatabase < SimpleDelegator</span>
<span class='line line-2 ' > def convert(table: table, column: column, to: type)</span>
<div class='lines-callout'><span class='line line-3 line-callout' > @conversions[table][column] = type</span>
</div><span class='line line-4 ' > end</span>
<span class='line line-5 ' >end</span>
<span class='line line-6 ' >$database = WrappingDatabase.new($database)</span>
<span class='line line-7 ' ></span>
<span class='line line-8 ' >$database.convert table: :addresses, </span>
<span class='line line-9 ' > column: :zip_code, </span>
<span class='line line-10 ' > to: ZipCode</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >class WrappingDatabase < SimpleDelegator</span>
<span class='line line-2 ' > def select_from(table, where)</span>
<span class='line line-3 ' > raw_results = __getobj__.select_from(table,where)</span>
<span class='line line-4 ' > convert_results(table,raw_results)</span>
<span class='line line-5 ' > end</span>
<span class='line line-6 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >def convert_results(table,raw_results)</span>
<span class='line line-2 ' > raw_results.map { |row_hash|</span>
<span class='line line-3 ' > convert_row(table,row_hash)</span>
<span class='line line-4 ' > }</span>
<span class='line line-5 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >def convert_row(table,row_hash)</span>
<span class='line line-2 ' > row_as_array = row_hash.map { |column,value|</span>
<span class='line line-3 ' > new_value = if @conversions[table][column]</span>
<span class='line line-4 ' > # e.g. ZipCode.new("90210")</span>
<span class='line line-5 ' > @conversions[table][column].new(value)</span>
<span class='line line-6 ' > else</span>
<span class='line line-7 ' > value</span>
<span class='line line-8 ' > end</span>
<span class='line line-9 ' > [column,new_value]</span>
<span class='line line-10 ' > }</span>
<span class='line line-11 ' > row_as_array.to_h</span>
<span class='line line-12 ' >end</span>
<span class='line line-13 ' ></span></code></pre>
</section>
<section class='NORMAL'>
<h1>Active Record</h1>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >class Address < ActiveRecord::Base</span>
<span class='line line-2 ' > serialize :zip_code, ZipCode</span>
<span class='line line-3 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >class ZipCode</span>
<span class='line line-2 ' > def self.load(raw_string)</span>
<span class='line line-3 ' > self.new(raw_string)</span>
<span class='line line-4 ' > end</span>
<span class='line line-5 ' ></span>
<span class='line line-6 ' > def self.dump(zip_code)</span>
<span class='line line-7 ' > zip_code.to_str</span>
<span class='line line-8 ' > end</span>
<span class='line line-9 ' >end</span></code></pre>
</section>
<section class='CODE'>
<pre><code class='none' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >address = Address.find(43) # has the bad zipcode</span>
<span class='line line-2 ' ><ArgumentError "must be a ZipCode"></span></code></pre>
</section>
<section class='NORMAL'>
<h1>Sequel</h1>
</section>
<section class='CODE'>
<pre><code class='ruby' data-strikeouts='' data-callout-lines=''><span class='line line-1 ' >require 'sequel/plugins/serialization'</span>
<span class='line line-2 ' >Sequel::Plugins::Serialization.register_format(:zip_code_serialization,</span>
<span class='line line-3 ' > ->(zip_code) { zip_code.to_str },</span>
<span class='line line-4 ' > ->(raw_string) { ZipCode.new(raw_string) }</span>
<span class='line line-5 ' >)</span>
<span class='line line-6 ' ></span>
<span class='line line-7 ' >class Address < Sequel::Model</span>
<span class='line line-8 ' > plugin :serialization</span>
<span class='line line-9 ' > serialize_attributes :zip_code_serialization, :zip_code</span>
<span class='line line-10 ' >end</span></code></pre>
</section>
<section class='SECTION'>
<h1>Other Opportunites</h1>
</section>
<section class='NORMAL'>
<h1>Email</h1>
<h2><code>EmailAddress</code>, <code>VerifiedEmailAddress</code></h2>
</section>
<section class='COMMANDLINE'>
<pre><code class='no-highlight'><span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> "[email protected]" == "[email protected]"</span>
<span class='cli-element cli-result'><span class='cli-line'> => false </span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> "[email protected]".downcase == "[email protected]".downcase #sigh</span>
<span class='cli-element cli-result'><span class='cli-line'> => true </span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> EmailAddress.new("[email protected]") == EmailAddress.new("[email protected]")</span>
<span class='cli-element cli-result'><span class='cli-line'> => true</span></span>
</code></pre>
</section>
<section class='NORMAL'>
<h1>Prices</h1>
</section>
<section class='COMMANDLINE'>
<pre><code class='no-highlight'><span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> third = Rational(1,3)</span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> (100 * third).to_f</span>
<span class='cli-element cli-result'><span class='cli-line'>33.333333333336</span></span>
<span class='cli-prompt'>></span> <span class='cli-element cli-command cli-line'> Price.new(100).discount(third) </span>
<span class='cli-element cli-result'><span class='cli-line'><Price value=33.33></span>
<span class='cli-line'></span></span>
</code></pre>
</section>
<section class='NORMAL'>
<h1>Enumerated Types</h1>
<h2>State/Province, Status Codes, Error Codes</h2>
</section>
<section class='SECTION'>
<h1>Use Data Types</h1>
<h2>Define Your Boundaries</h2>
<h3>Put Your Knowledge and Intent in Code</h3>
</section>
<section class='FREEFORM'>
<h1>THANKS!</h1>
<h2><a href="#">Slides</a></h2>
<h3><a href="http://www.naildrivin5.com/blog">My Blog - http://www.naildrivin5.com/blog</a></h3>
<h4><a href="http://technology.stitchfix.com/jobs">Get A New Job at http://technology.stitchfix.com/jobs</a></h4>
</section>
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