JavaScript接口实现代码 （Interfaces In JavaScript）
发布时间：2016-11-24 03:50:48 所属栏目：Unix 来源：站长网
导读：在实际中，我们可以在注释中定义好接口，在实际的代码中予以实现 比如： 复制代码 代码如下: /* interface Composite { function add(child); function remove(child); function getChild(index); } interface FormItem { function save(); } */ var Compos
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在实际中，我们可以在注释中定义好接口，在实际的代码中予以实现 比如： 复制代码 代码如下: /* interface Composite { function add(child); function remove(child); function getChild(index); } interface FormItem { function save(); } */ var CompositeForm = function(id, method, action) { // implements Composite, FormItem ... }; // Implement the Composite interface. CompositeForm.prototype.add = function(child) { ... }; CompositeForm.prototype.remove = function(child) { ... }; CompositeForm.prototype.getChild = function(index) { ... }; // Implement the FormItem interface. CompositeForm.prototype.save = function() { ... }; 实现接口的程序员是否将这些接口都实现了呢？我们没办法保证！因为这里没有任何办法去检查是否都实现了 我们需要一个检查是否实现了接口的机制，可以这样： 复制代码 代码如下: /* interface Composite { function add(child); function remove(child); function getChild(index); } interface FormItem { function save(); } */ var CompositeForm = function(id, method, action) { this.implementsInterfaces = ['Composite', 'FormItem']; ... }; ... function addForm(formInstance) { if(!implements(formInstance, 'Composite', 'FormItem')) { throw new Error("Object does not implement a required interface."); } ... } // The implements function, which checks to see if an object declares that it // implements the required interfaces. function implements(object) { for(var i = 1; i lt; arguments.length; i++) { // Looping through all arguments // after the first one. var interfaceName = arguments[i]; var interfaceFound = false; for(var j = 0; j lt; 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. } 这种方法让程序员在写的时候注明实现了哪些接口： this.implementsInterfaces = ['Composite', 'FormItem']; 在调用的时候使用implements方法来判断是否实现了，理论上可行，很有可能写上了实现了'Composite'接口，但是代码里却并没有add方法！因此，我们需要检验实现接口的类是否包含了接口里的方法！所以，接口必须从注释中解放出来： 复制代码 代码如下: // Interfaces. var Composite = new Interface('Composite', ['add', 'remove', 'getChild']); var FormItem = new Interface('FormItem', ['save']); // CompositeForm class var CompositeForm = function(id, method, action) { // implements Composite, FormItem ... }; ... function addForm(formInstance) { Interface.ensureImplements(formInstance, Composite, FormItem); // This function will throw an error if a required method is not implemented, // halting execution of the function. // All code beneath this line will be executed only if the checks pass. ... } 定义接口Composite，FormItem，并且CompositeForm实现这两个接口，在使用的时候，用Interface.ensureImplements来检验formInstance是否实现了这两个接口中的所有方法。 来看看Interface的定义：两个参数，第一个参数是接口名称，第二个参数是接口包含的方法数组 复制代码 代码如下: // Constructor. var Interface = function(name, methods) { if(arguments.length != 2) { throw new Error("Interface constructor called with " + arguments.length + "arguments, but expected exactly 2."); } this.name = name; this.methods = []; for(var i = 0, len = methods.length; i lt; len; i++) { if(typeof methods[i] !== 'string') { throw new Error("Interface constructor expects method names to be " + "passed in as a string."); } this.methods.push(methods[i]); } }; 为Interface 添加建议接口是否实现的静态方法 复制代码 代码如下: // Constructor. Interface.ensureImplements = function(object) { if(arguments.length lt; 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 lt; len; i++) { var interface = arguments[i]; if(interface.constructor !== Interface) { throw new Error("Function Interface.ensureImplements expects arguments" + "two and above to be instances of Interface."); } for(var j = 0, methodsLen = interface.methods.length; j lt; 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."); } } } }; （编辑：淮北站长网） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |
