JavaScript接口实现代码 (Interfaces In JavaScript)


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 < 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.
}

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 < 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 < 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++) {
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 < 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.");
}
}
}
};



相关阅读:
基于jquery的当鼠标滚轮到最底端继续加载新数据思路分享(多用于微博、空间、论坛 )
mysql错代码与解决方法
php expects parameter 1 to be resource, array given 错误
ASP.NET中实现模板页
Linux系统安全的九大技巧
CSS 图片横向排列实现代码
没有光驱利用U盘安装Windows7、Vista及安装盘的制作方法
vbs 获取radmin注册表中的信息
JavaScript中的Screen屏幕对象
存储过程中的top+变量(downmoon)
在批处理文件或配置文件中加入注释
WINDOWS服务器安装多套PHP的另类解决方案
PHP4中session登录页面的应用
PHP:10个不常见却非常有用的PHP函数
快速导航

Copyright © 2016 phpStudy | 皖ICP备18014864号-4