javascript设计模式一——接口
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JavaScript是弱类型语言，所以类型匹配问题很难追踪。同时，Js并没有像其他语言一样，提供内置的创建或实现接口的方法。这样，在我们进行对象转化的时候是很困难的。
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不过，我们还是可以使用程序来模拟JavaScript Interface接口的实现。一般来说，模拟Interface的实现有如下三种方法：
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注释法——将接口的定义写在注释中，大家能否小心注意，以实现接口的所有方法全凭自觉。
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java中使用interface和implements关键字实现接口的
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/*interface Composite{function add(child);function remove(child);function getChild(index);}interface FormItem{function save();}*/?
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//模拟CompositeForm继承了Composite、FormItem接口var CompositeForm = function(id,name,action){...}CompositeForm.prototype = {add:function(child){...},remove:function(child){...},getChild:function(index){...},save:function(){...}}?
备注：这种模仿并不是很好，它没有为确保CompositeForm真正实现了正确的方法集而进行检查，也不会抛出错误以告知程序中有问题。
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属性检查法——自己说明我实现了哪些接口，一会儿你检查的时候记得检查我说我实现的接口里面，是否把我真正想要实现的接口全部实现了（这么别扭呢），总之就是自欺欺人
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var CompositeForm = function(id, method, action) { //声明自己继承了Composite，FormItem接口 this.implementsInterfaces = ['Composite', 'FormItem']; ...};function addForm(formInstance) { //判断formInstance是否继承了Composite，FormItem接口 if(!implements(formInstance, 'Composite', 'FormItem')) { throw new Error("Object does not implement a required interface."); } ...}//判断当前对象是否继承了对象声明的接口function implements(object) { for(var i = 1; i < arguments.length; i++) { // Looping through all arguments // after the first one. var interfaceName = arguments[i]; var interfaceFound = false; for(var j = 0; j < object.implementsInterfaces.length; j++) { if(object.implementsInterfaces[j] == interfaceName) { interfaceFound = true; break; } } if(!interfaceFound) { return false; // An interface was not found. } } return true; // All interfaces were found.}?
鸭式辨型法——如果对象具有与接口定义的方法同名的所有方法，那么久可以认为它实现了这个接口。
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var Interface = function(name,methods){if(arguments.length!=2){throw new Error("Interface 的构造函数一定只能有两个参数")}this.name = name;this.methods = [];for(var i=0,len=methods.length;i<len;i++){if(typeof methods[i] !== "string"){throw new Error("Interface构造参数方法名称为string类型");}else{this.methods.push(methods[i]);}}}Interface.ensureImplements = function(object){//至少包含两个参数——继承接口的对象，对应的接口（至少含有一个）if(arguments.length<2){throw new Error("Function Interface.ensureImplements called with " + arguments.length + "arguments, but expected at least 2.");}for(var i=1,len=arguments.length;i<len;i++){//具体实现接口的对象var _interface = arguments[i];if(_interface.constructor !== Interface) { throw new Error("Function Interface.ensureImplements expects arguments " + "two and above to be instances of Interface."); }//接口对应的参数for(var j = 0, methodsLen = _interface.methods.length; j < methodsLen; j++) {var method = _interface.methods[j]; if(!object[method] || typeof object[method] !== 'function') { throw new Error("Function Interface.ensureImplements: object " + "does not implement the " + _interface.name + " interface. Method " + method + " was not found."); }}}}var Composite = new Interface("Composite",["add","remove","getChild"]);var FormItem = new Interface("FormItem",["save"]);//CompositeForm继承Composite、FormItem两个接口/*提示缺少接口对象参数var CompositeForm = new function(id, method, action){}Interface.ensureImplements(CompositeForm);*//*提示没有实现Composite接口var CompositeForm = new function(id, method, action){}Interface.ensureImplements(CompositeForm,Composite);*//*提示没有实现Composite接口var CompositeForm = new function(id, method, action){this.add=function(){};this.remove=function(){};//this.getChild=function(){};}Interface.ensureImplements(CompositeForm,Composite);*//*正确显示var CompositeForm = new function(id, method, action){this.add=function(){};this.remove=function(){};this.getChild=function(){};}Interface.ensureImplements(CompositeForm,Composite);*//*var CompositeForm = new function(id, method, action){this.add=function(){};this.remove=function(){};this.getChild=function(){};this.save=function(){};}Interface.ensureImplements(CompositeForm,Composite,FormItem);*/var CompositeForm = new function(id, method, action){this.add=function(){};this.remove=function(){};this.getChild=function(){};this.save=function(){};//用来验证当前对象是否实现了Composite,FormItem接口Interface.ensureImplements(this,Composite,FormItem);}?
?教程上的另外一个例子
ResultFormatter.prototype.renderResults = function() { var dateOfTest = this.resultsObject.getDate(); var resultsArray = this.resultsObject.getResults(); var resultsContainer = document.createElement('div'); var resultsHeader = document.createElement('h3'); resultsHeader.innerHTML = 'Test Results from ' + dateOfTest.toUTCString(); resultsContainer.appendChild(resultsHeader); var resultsList = document.createElement('ul'); resultsContainer.appendChild(resultsList); for(var i = 0, len = resultsArray.length; i < len; i++) { var listItem = document.createElement('li'); listItem.innerHTML = resultsArray[i]; resultsList.appendChild(listItem); } return resultsContainer;};// ResultSet Interface.var ResultSet = new Interface('ResultSet', ['getDate', 'getResults']);// ResultFormatter class, after adding Interface checking.var ResultFormatter = function(resultsObject) { Interface.ensureImplements(resultsObject, ResultSet); this.resultsObject = resultsObject;};?