在Javascript中模仿接口（一） | 小胡子哥的个人网站

本文从ITeye导入

在JavaScript中模仿接口——本文摘自《JavaScript设计模式》

一、用注释描述接口

/*
    interface Composite {
        function add(child);
        function remove(child);
        function getChild(index);
    }

    interface FormItem {
        function save();
    }
*/

var CompositeForm = function(id, method, action){
    //......
};

//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(){
    //......
}

这种模仿并不是很好，他们有为确保CompositeForm真正实现正确的方法集而进行检查，

也不会跑出错误以高质程序员程序中的问题。

二、用属性检查模仿接口

/*
        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 delcares that it
    //implements the required interfaces.

    function implements(object){
        for(var i = 0; i < arguments.length; i++){
            var interfaceName = arguments[i];
            var interfaceFound = false;
            for(var j = 0; j < object.implementsInterface.length; j++){
                if(object.implementsInterface[j] == interfaceName){
                    interfaceFound = true;
                    break;
                }
            }
            if(!interfaceFound){
                return false; //An interface was not found.
            }
        }
        return true; //All interface were found.
    }

在这个例子中，CompositeForm宣传自己实现了Composite和FormItem这两个接口，其做法是吧这链各个接口的

名称加入一个名为implement上Interfaces的数组。

三、用鸭式辨型模仿接口

//Interfaces

var composite = new Interface('Composite', ['add', 'remove', 'getChild']);
var FormItem = new Interface('FormItem', ['save']);

//CompositeForm class
var CompositeForm = function(id, method, action){
    //........
}

function addForm(formInstancd){
    ensureImplements(formInstance, Composite, FormItem);
    //........
}

待续......