javascript面向对象编程（三）
[Interface,Class.implement 接口及实现]
接口规定了一些方法，如果一个类实现了接口所定义的所有方法，就叫做实现了这个接口。诚然，javascript来模拟接口会带来一些效率上的损失，但是在大型项目特别是团队开发的时候，接口将带来很大的方便。使项目代码更加规范，更方便地查找错误信息。很多设计模式，像工厂模式、合成模式、装饰模式、命令模式等都依赖于接口来实现。
javascript模拟接口包括两部分:接口的模拟和接口实现的模拟。
[Interface接口类]
这段代码定义一个接口类，同样来自于《javascript design patterns》，略有改动。
Actionscript:
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// Constructor.
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var Interface = function(name, methods){
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if (arguments.length != 2) {
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throw new Error("Interface constructor called with " + arguments.length +
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"arguments, but expected exactly 2.");
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}
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this.name = name;
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this.methods = [];
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for (var i = 0, len = methods.length; i <len; i++) {
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if (typeof methods[i] !== 'string') {
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throw new Error("Interface constructor expects method names to be " +
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"passed in as a string.");
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}
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this.methods.push(methods[i]);
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}
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};
[Interface.ensureImplements 接口实现检查]
这段代码检查一个对象是否实现了所要实现接口。
Actionscript:
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// Static class method.
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Interface.ensureImplements = function(object){
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if (arguments.length <2) {
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throw new Error('Interface.ensureImplements:Wrong arguments number');
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}
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for (var i = 1, len = arguments.length; i <len; i++) {
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var interfaces = arguments[i];
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if (interfaces.constructor !== Interface) {
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throw new Error("Function Interface.ensureImplements expects arguments " +
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"two and above to be instances of Interface.");
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}
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for (var j = 0, methodLen = interfaces.methods.length; j <methodLen; j++) {
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var method = interfaces.methods[j];
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if (!object.prototype[method] || typeof(object.prototype[method]) !== 'function') {
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throw new Error("Function Interface.ensureImplements: object " +
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"does not implement the " +
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interfaces.name +
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" interface. Method " +
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method +
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" was not found.");
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}
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}
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}
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}
[Class.implement类实现接口]
接口定义后，还不能带来任何好处，需要在类中体现出来。看下面的两段代码就很清楚了：程序演示页面(3)
JavaScript:
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
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<script language="JavaScript" src="http://rssidea.com/labs/OOP/OOP.js"></script>
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<title>labs@RSSIDEA javascript OOP</title>
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</head>
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<body>
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<script language="JavaScript">
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//定义一个computer的接口，要求实现motherborad,memory,cpu,harddisk的方法。
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var computer = new Interface('computer', ['motherboard', 'memory', 'cpu', 'harddisk'])
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//定义一个PC类，实现computer接口
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var PC = Class.create({
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motherboardInfo: '',
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memoryInfo: '',
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cpuInfo: '',
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harddiskInfo: '',
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init: function(motherboard, memory, cpu, harddisk){
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this.motherboardInfo = motherboard;
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this.memoryInfo = memory;
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this.cpuInfo = cpu;
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this.harddiskInfo = harddisk;
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},
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motherboard: function(){
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return this.motherboardInfo;
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},
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memory: function(){
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return this.memoryInfo;
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},
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cpu: function(){
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return this.cpuInfo;
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},
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mouse:function(){
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return this.mouseInfo;
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}
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}).implement(computer);//浏览器报错,(没有硬盘电脑怎么转啊?)
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var myComputer = new PC('微星主板', '现代2G', 'AMD3600+', '三星80G');
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//输出电脑配置信息
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trace(myComputer);
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</script>
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</body>
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</html>
但是这段代码我们却得到一个浏览器错误，方法harddisk没有实现。（没有硬盘叫什么电脑啊？）
好吧，好吧！我承认是我拿买硬盘的钱去买了一个鼠标……（这鼠标不错吧？）
我原以为可以混过去，却被检查出来了。接口的工作和作用和上面的情况类似。现在，我需要再买个硬盘（harddisk）。程序演示页面(4)
JavaScript:
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
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<script language="JavaScript" src="http://rssidea.com/labs/OOP/OOP.js"></script>
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<title>labs@RSSIDEA javascript OOP</title>
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</head>
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<body>
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<script language="JavaScript">
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//定义一个computer的接口，要求实现motherborad,memory,cpu,harddisk的方法。
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var computer = new Interface('computer', ['motherboard', 'memory', 'cpu', 'harddisk'])
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//定义一个PC类，实现computer接口
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var PC = Class.create({
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motherboardInfo: '',
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memoryInfo: '',
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cpuInfo: '',
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harddiskInfo: '',
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init: function(motherboard, memory, cpu, harddisk){
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this.motherboardInfo = motherboard;
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this.memoryInfo = memory;
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this.cpuInfo = cpu;
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this.harddiskInfo = harddisk;
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},
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motherboard: function(){
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return this.motherboardInfo;
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},
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memory: function(){
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return this.memoryInfo;
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},
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cpu: function(){
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return this.cpuInfo;
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},
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mouse:function(){
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return this.mouseInfo;
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},
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harddisk:function(){
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return this.harddiskInfo;
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}//这是新买的硬盘
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}).implement(computer);//实现了computer接口
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var myComputer = new PC('微星主板', '现代2G', 'AMD3600+', '三星80G');
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//输出电脑配置信息
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trace(myComputer);
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</script>
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</body>
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</html>
太好了！浏览器不再报错，这样，我们就实现了computer接口。
