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class.js
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class.js
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/* Based on Alex Arnell's inheritance implementation. */
/** section: Language
* Class
*
* Manages Prototype's class-based OOP system.
*
* Refer to Prototype's web site for a [tutorial on classes and
* inheritance](http://prototypejs.org/learn/class-inheritance).
**/
var Class = (function() {
/**
* Class.create([superclass][, methods...]) -> Class
* - superclass (Class): The optional superclass to inherit methods from.
* - methods (Object): An object whose properties will be "mixed-in" to the
* new class. Any number of mixins can be added; later mixins take
* precedence.
*
* Creates a class.
*
* Class.create returns a function that, when called, will fire its own
* `initialize` method.
*
* `Class.create` accepts two kinds of arguments. If the first argument is
* a `Class`, it's treated as the new class's superclass, and all its
* methods are inherited. Otherwise, any arguments passed are treated as
* objects, and their methods are copied over as instance methods of the new
* class. Later arguments take precedence over earlier arguments.
*
* If a subclass overrides an instance method declared in a superclass, the
* subclass's method can still access the original method. To do so, declare
* the subclass's method as normal, but insert `$super` as the first
* argument. This makes `$super` available as a method for use within the
* function.
*
* To extend a class after it has been defined, use [[Class#addMethods]].
**/
function subclass() {};
function create() {
var parent = null, properties = $A(arguments);
if (Object.isFunction(properties[0]))
parent = properties.shift();
function klass() {
this.initialize.apply(this, arguments);
}
Object.extend(klass, Class.Methods);
klass.superclass = parent;
klass.subclasses = [];
if (parent) {
subclass.prototype = parent.prototype;
klass.prototype = new subclass;
parent.subclasses.push(klass);
}
for (var i = 0; i < properties.length; i++)
klass.addMethods(properties[i]);
if (!klass.prototype.initialize)
klass.prototype.initialize = Prototype.emptyFunction;
klass.prototype.constructor = klass;
return klass;
}
/**
* Class#addMethods(methods) -> Class
* - methods (Object): The methods to add to the class.
*
* Adds methods to an existing class.
*
* `Class#addMethods` is a method available on classes that have been
* defined with `Class.create`. It can be used to add new instance methods
* to that class, or overwrite existing methods, after the class has been
* defined.
*
* New methods propagate down the inheritance chain. If the class has
* subclasses, those subclasses will receive the new methods — even in the
* context of `$super` calls. The new methods also propagate to instances of
* the class and of all its subclasses, even those that have already been
* instantiated.
*
* <h4>Examples</h4>
*
* var Animal = Class.create({
* initialize: function(name, sound) {
* this.name = name;
* this.sound = sound;
* },
*
* speak: function() {
* alert(this.name + " says: " + this.sound + "!");
* }
* });
*
* // subclassing Animal
* var Snake = Class.create(Animal, {
* initialize: function($super, name) {
* $super(name, 'hissssssssss');
* }
* });
*
* var ringneck = new Snake("Ringneck");
* ringneck.speak();
*
* //-> alerts "Ringneck says: hissssssss!"
*
* // adding Snake#speak (with a supercall)
* Snake.addMethods({
* speak: function($super) {
* $super();
* alert("You should probably run. He looks really mad.");
* }
* });
*
* ringneck.speak();
* //-> alerts "Ringneck says: hissssssss!"
* //-> alerts "You should probably run. He looks really mad."
*
* // redefining Animal#speak
* Animal.addMethods({
* speak: function() {
* alert(this.name + 'snarls: ' + this.sound + '!');
* }
* });
*
* ringneck.speak();
* //-> alerts "Ringneck snarls: hissssssss!"
* //-> alerts "You should probably run. He looks really mad."
**/
function addMethods(source) {
var ancestor = this.superclass && this.superclass.prototype;
var properties = Object.keys(source);
// IE6 doesn't enumerate toString and valueOf properties,
// Force copy if they're not coming from Object.prototype.
if (!Object.keys({ toString: true }).length) {
if (source.toString != Object.prototype.toString)
properties.push("toString");
if (source.valueOf != Object.prototype.valueOf)
properties.push("valueOf");
}
for (var i = 0, length = properties.length; i < length; i++) {
var property = properties[i], value = source[property];
if (ancestor && Object.isFunction(value) &&
value.argumentNames().first() == "$super") {
var method = value;
value = (function(m) {
return function() { return ancestor[m].apply(this, arguments); };
})(property).wrap(method);
value.valueOf = method.valueOf.bind(method);
value.toString = method.toString.bind(method);
}
this.prototype[property] = value;
}
return this;
}
return {
create: create,
Methods: {
addMethods: addMethods
}
};
})();