✨ Add Optional value-wrapper class

CHANGELOG.md

@@ -13,6 +13,7 @@
 * Fix comments breaking the SSE request handler
 * Add `Blast.isAppleWebkit` boolean
 * Add `Blast.environment` string property and `isProduction`, `isDevelopment` and `isStaging` booleans
+* Add `Optional` value-wrapper class
 
 ## 0.9.2 (2024-02-25)
 

lib/init.js

@@ -483,6 +483,7 @@ function BlastInit(modifyPrototype) {
 		'Error',
 		'Placeholder',
 		'Trail',
+		'Optional',
 		'Informer',
 		'State',
 		'Request',

lib/optional.js

@@ -0,0 +1,134 @@
+const VALUE = Symbol('value'),
+      CALLBACKS = Symbol('callbacks');
+
+/**
+ * An optional value
+ *
+ * @constructor
+ *
+ * @author   Jelle De Loecker <[email protected]>
+ * @since    0.9.3
+ * @version  0.9.3
+ *
+ * @param    {*}   value
+ */
+const Optional = Fn.inherits('Develry.Placeholder', function Optional(value) {
+	this[VALUE] = value;
+	this[CALLBACKS] = [];
+});
+
+/**
+ * Undry the value
+ *
+ * @author   Jelle De Loecker <[email protected]>
+ * @since    0.9.3
+ * @version  0.9.3
+ *
+ * @param    {Object}   value
+ *
+ * @return   {Optional}
+ */
+Optional.setStatic(function unDry(value) {
+	let result = Object.create(this.prototype);
+	result[VALUE] = value.value;
+	return result;
+});
+
+/**
+ * Get the current value
+ *
+ * @author   Jelle De Loecker <[email protected]>
+ * @since    0.9.3
+ * @version  0.9.3
+ *
+ * @return   {*}
+ */
+Optional.setProperty(function value() {
+	return this[VALUE];
+}, function setValue(new_value) {
+	this[VALUE] = new_value;
+
+	let callbacks = this[CALLBACKS],
+	    i;
+
+	for (i = 0; i < callbacks.length; i++) {
+		callbacks[i](new_value);
+	}
+});
+
+/**
+ * Return the serialized json-dry representation
+ *
+ * @author   Jelle De Loecker <[email protected]>
+ * @since    0.9.3
+ * @version  0.9.3
+ */
+Optional.setMethod(function toDry() {
+
+	let value = {
+		value: this[VALUE]
+	};
+
+	return {
+		value: value
+	};
+});
+
+/**
+ * Add a listener
+ *
+ * @author   Jelle De Loecker <[email protected]>
+ * @since    0.9.3
+ * @version  0.9.3
+ *
+ * @param    {Function}   callback
+ */
+Optional.setMethod(function onChange(callback) {
+	this[CALLBACKS].push(callback);
+});
+
+/**
+ * Is there a value present?
+ *
+ * @author   Jelle De Loecker <[email protected]>
+ * @since    0.9.3
+ * @version  0.9.3
+ *
+ * @return   {boolean}
+ */
+Optional.setMethod(function isPresent() {
+	return this[VALUE] != null;
+});
+
+/**
+ * Get the current value if it is present of the given fallback value if it is not
+ *
+ * @author   Jelle De Loecker <[email protected]>
+ * @since    0.9.3
+ * @version  0.9.3
+ *
+ * @param    {*}   fallback
+ *
+ * @return   {*}
+ */
+Optional.setMethod(function orElse(fallback) {
+
+	if (this.isPresent()) {
+		return this[VALUE];
+	}
+
+	return fallback;
+});
+
+/**
+ * This method should return the actual value
+ *
+ * @author   Jelle De Loecker <[email protected]>
+ * @since    0.9.3
+ * @version  0.9.3
+ *
+ * @return   {*}
+ */
+Optional.setMethod(function getResolvedValue() {
+	return this[VALUE];
+});