一个javascript继承的基础类Base.js
一个javascript继承的基础类Base.js
官网:http://dean.edwards.name
http://dean.edwards.name/weblog/2006/03/base/
一个javascript继承的基础类
首先我是一个面向对象的程序员,并且javascript支持prototype 方式继承,例如:
function Animal(name) {};
Animal.prototype.eat = function() {};
Animal.prototype.say = function(message) {};
我想要一个更漂亮的基类,来实现javascript的面相对象.
1.我想不用prototype并容易地创建类.
2.我想用一个方法重写父类方法,就像java支持的那样.
3.在原型阶段我想要避免调用一个类的构造函数函数.
4.我想在类上容易的创建静态方法或属性.
5.我想实现上述功能不用全局函数
6.我想实现上诉功能不影响Object.prototype
/*
Base.js, version 1.1a
Copyright 2006-2010, Dean Edwards
License: http://www.opensource.org/licenses/mit-license.php
*/
var Base = function() {
// dummy
};
Base.extend = function(_instance, _static) { // subclass
var extend = Base.prototype.extend;
// build the prototype
Base._prototyping = true;
var proto = new this;
extend.call(proto, _instance);
proto.base = function() {
// call this method from any other method to invoke that method's ancestor
};
delete Base._prototyping;
// create the wrapper for the constructor function
//var constructor = proto.constructor.valueOf(); //-dean
var constructor = proto.constructor;
var klass = proto.constructor = function() {
if (!Base._prototyping) {
if (this._constructing || this.constructor == klass) { // instantiation
this._constructing = true;
constructor.apply(this, arguments);
delete this._constructing;
} else if (arguments[0] != null) { // casting
return (arguments[0].extend || extend).call(arguments[0], proto);
}
}
};
// build the class interface
klass.ancestor = this;
klass.extend = this.extend;
klass.forEach = this.forEach;
klass.implement = this.implement;
klass.prototype = proto;
klass.toString = this.toString;
klass.valueOf = function(type) {
//return (type == "object") ? klass : constructor; //-dean
return (type == "object") ? klass : constructor.valueOf();
};
extend.call(klass, _static);
// class initialisation
if (typeof klass.init == "function") klass.init();
return klass;
};
Base.prototype = {
extend: function(source, value) {
if (arguments.length > 1) { // extending with a name/value pair
var ancestor = this[source];
if (ancestor && (typeof value == "function") && // overriding a method?
// the valueOf() comparison is to avoid circular references
(!ancestor.valueOf || ancestor.valueOf() != value.valueOf()) &&
/\bbase\b/.test(value)) {
// get the underlying method
var method = value.valueOf();
// override
value = function() {
var previous = this.base || Base.prototype.base;
this.base = ancestor;
var returnValue = method.apply(this, arguments);
this.base = previous;
return returnValue;
};
// point to the underlying method
value.valueOf = function(type) {
return (type == "object") ? value : method;
};
value.toString = Base.toString;
}
this[source] = value;
} else if (source) { // extending with an object literal
var extend = Base.prototype.extend;
// if this object has a customised extend method then use it
if (!Base._prototyping && typeof this != "function") {
extend = this.extend || extend;
}
var proto = {toSource: null};
// do the "toString" and other methods manually
var hidden = ["constructor", "toString", "valueOf"];
// if we are prototyping then include the constructor
var i = Base._prototyping ? 0 : 1;
while (key = hidden[i++]) {
if (source[key] != proto[key]) {
extend.call(this, key, source[key]);
}
}
// copy each of the source object's properties to this object
for (var key in source) {
if (!proto[key]) extend.call(this, key, source[key]);
}
}
return this;
}
};
// initialise
Base = Base.extend({
constructor: function() {
this.extend(arguments[0]);
}
}, {
ancestor: Object,
version: "1.1",
forEach: function(object, block, context) {
for (var key in object) {
if (this.prototype[key] === undefined) {
block.call(context, object[key], key, object);
}
}
},
implement: function() {
for (var i = 0; i < arguments.length; i++) {
if (typeof arguments[i] == "function") {
// if it's a function, call it
arguments[i](this.prototype);
} else {
// add the interface using the extend method
this.prototype.extend(arguments[i]);
}
}
return this;
},
toString: function() {
return String(this.valueOf());
}
});
extend
var object = new Base;
object.extend({
value: "some data",
method: function() {
alert("Hello World!");
}
});
object.method();
// ==> Hello World!
base
var object = new Base;
object.method = function() {
alert("Hello World!");
};
object.extend({
method: function() {
// call the "super" method
this.base();
// add some code
alert("Hello again!");
}
});
object.method();
// ==> Hello World!
// ==> Hello again!
Creating Classes
var Animal = Base.extend({
constructor: function(name) {
this.name = name;
},
name: "",
eat: function() {
this.say("Yum!");
},
say: function(message) {
alert(this.name + ": " + message);
}
});
var Cat = Animal.extend({
eat: function(food) {
if (food instanceof Mouse) this.base();
else this.say("Yuk! I only eat mice.");
}
});
var Mouse = Animal.extend();