Cocos2d-JS中JavaScript继承，cocos2djs继承
JavaScript语言本身没有提供类，没有其它语言的类继承机制，它的继承是通过对象的原型实现的，但这不能满足Cocos2d-JS引擎的要求。由于Cocos2d-JS引擎是从Cocos2d-x演变而来的，在Cocos2d-JS的早期版本Cocos2d-HTML中几乎全部的API都是模拟Cocos2d-x API而设计的，Cocos2d-x本身是有C++编写的，其中的很多对象和函数比较复杂，JavaScript语言描述起来有些力不从心了。在开源社区中John Resiq在他的博客（http://ejohn.org/blog/simple-javascript-inheritance/）中提供了一种简单JavaScript继承（Simple JavaScript Inheritance）方法。John Resiq的简单JavaScript继承方法灵感来源于原型继承机制，它具有与Java等面向对象一样的类概念，并且他设计了所有类的根类Class，它的代码如下：/* Simple JavaScript Inheritance
* By John Resig http://ejohn.org/
* MIT Licensed.
*/
// Inspired by base2 and Prototype
(function(){
var initializing = false, fnTest = /xyz/.test(function(){xyz;}) ? /\b_super\b/ : /.*/;
// The base Class implementation (does nothing)
this.Class = function(){};
// Create a new Class that inherits from this class
Class.extend = function(prop) {
var _super = this.prototype;
// Instantiate a base class (but only create the instance,
// don't run the init constructor)
initializing = true;
var prototype = new this();
initializing = false;
// Copy the properties over onto the new prototype
for (var name in prop) {
// Check if we're overwriting an existing function
prototype[name] = typeof prop[name] == "function" &&
typeof _super[name] == "function" && fnTest.test(prop[name]) ?
(function(name, fn){
return function() {
var tmp = this._super;
// Add a new ._super() method that is the same method
// but on the super-class
this._super = _super[name];
// The method only need to be bound temporarily, so we
// remove it when we're done executing
var ret = fn.apply(this, arguments);
this._super = tmp;
return ret;
};
})(name, prop[name]) :
prop[name];
}
// The dummy class constructor
function Class() {
// All construction is actually done in the init method
if ( !initializing && this.init )
this.init.apply(this, arguments);
}
// Populate our constructed prototype object
Class.prototype = prototype;
// Enforce the constructor to be what we expect
Class.prototype.constructor = Class;
// And make this class extendable
Class.extend = arguments.callee;
return Class;
};
})();
与Java中的Object一样所有类都直接或间接继承于Class，下面是继承Class实例：var Person = Class.extend({①
init: function (isDancing) {②
this.dancing = isDancing;
},
dance: function () {③
return this.dancing;
}
});
var Ninja = Person.extend({④
init: function () {⑤
this._super(false);⑥
},
dance: function () {⑦
// Call the inherited version of dance()
return this._super();⑧
},
swingSword: function () {⑨
return true;
}
});
var p = new Person(true);⑩
console.log(p.dance());// true
