创建模块化模式对象的继承 [英] Creating inheritance on revealing modular pattern objects

问题描述

我正在尝试在对象之间创建某种继承：

I'm trying to create some kind of inheritance between objects:

var foo = (function(){

    function doFooStuff(){
        console.log(arguments.callee.name);
    }

    return {
        doFooStuff: doFooStuff
    }

})();

var bar = (function(){

    $.extend(this, foo);

    function doBarStuff(){
        console.log(arguments.callee.name);
        doFooStuff();
    }

    return {
        doBarStuff: doBarStuff,
    }

})();

bar.doBarStuff();
bar.doFooStuff(); //<-- Uncaught TypeError: 
                  //Object #<Object> has no method 'doFooStuff' 

http://jsfiddle.net/wRXTv/

为什么不是 doFooStuff 可以在这里访问？你会推荐另一种方法，而不是使用 $ .extend ？

Why isn't doFooStuff accessible here? Would you recommend another approach than using $.extend?

推荐答案

$.extend(this, foo);

this 不是你从下面的函数返回的对象（实际上它不能是因为它是在这次调用之后创建的），而是全局对象 - 检查 MDN对这个关键字的介绍。

this is not the object which you return from the function below (in fact it cannot be since it's created after this call), but the global object - check MDN's introduction to the this keyword.

对于你想做的事，有两种方法：

For what you want to do, there are two ways:

• 将所有属性从 foo 复制到 bar 对象创建后：

• Copy all properties from foo onto your bar object after it is created:

var bar = (function() {
    …
    return {…};
})();
$.extend(bar, foo);

您也可以直接在返回的对象上执行此操作：

You can do that as well directly on the returned object:

    return $.extend({…}, foo);

此模式的变体允许您覆盖 foo 属性。将 foo 复制到一个空对象中，然后将 bar 属性写入其中：

A variant of this pattern allows you to overwrite foo properties. Copy foo into an empty object, then write your bar properties to it:

    return $.extend({}, foo, {…});

使用原型继承。 创建一个继承其属性的对象从 foo ，然后将 bar 属性写入其中：

Use prototypical inheritance. Create an object that inherits its properties from foo, and then write your bar properties to it:

    return $.extend(Object.create(foo), {…});

现在当 foo 之后发生变化时，你仍然可以在 bar 上访问这些新属性（除非它们被自己的属性遮蔽）。请注意，旧版环境可能不支持 Object.create ，但您可以轻松地将其填充。

Now when foo changes afterward, you still can access those new properties on bar (unless they're shadowed by own properties). Notice that Object.create might not be supported in legacy environments, but you can easily shim it.

如@ raina77ow所述，您的 doBarStuff 函数也存在缺陷。 doFooStuff 函数不在您的函数范围内，您无法更改它。您永远无法从 foo 模块访问私有声明的函数和变量，只能访问那些公开的函数和变量 - 如果确实需要它们，请考虑使用不同的模式或应用程序设计。但是， doFooStuff 是导出的（公共） foo 对象的属性，从该对象继承（无论哪个属性）以上说明的方法）。因此，您也可以通过使用 this.doFooStuff（）来访问它作为 bar 的方法。

As noted by @raina77ow, your doBarStuff function is flawed too. The doFooStuff function is not in the scope of your function, and you cannot change that. You never will be able to access the private declared functions and variables from the foo module, only those that are public - if you did need them, consider a different pattern or app design. However, doFooStuff is a property on the exported (public) foo object, from which bar inherits (regardless in which of the above demonstrated ways). Therefore, you can access it as a method of bar as well, usually by using this.doFooStuff().

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