(显示)模块模式，公共变量和返回语句 [英] (Revealing) Module Pattern, public variables and return-statement

问题描述

我试图了解(公开)模块模式中的 public`属性. Carl Danley"揭示模块模式" 是:

I'm trying to understand how public` properties in the (Revealing) Module Pattern work. An advantage pointed out by Carl Danley "The Revealing Module Pattern" is:

明确定义的公共方法和变量，从而提高了可读性

Explicitly defined public methods and variables which lead to increased readability

让我们看一下这段代码(小提琴):

Let's take a look at this code (fiddle):

var a = function() {
    var _private = null;
    var _public = null;
    function init() {
        _private = 'private';
        _public = 'public';
    }
    function getPrivate() {
        return _private;
    }
    return {
        _public : _public,
        init : init,
        getPrivate : getPrivate,
    }
}();

a.init();
console.log( a._public ); // null
console.log( a.getPrivate() ); // "private"

在调用a._public时返回null.我现在可以操纵该公共属性，例如a._public = 'public';.但是我不能从对象内部更改它.或至少这些更改没有通过.我有点期待它是"public"，因为它是以前通过init方法更新的.

It returns null when calling a._public. I now can manipulate that public property, like a._public = 'public';. But I can't change it from within my object. Or at least those changes aren't passed through. I was kinda expecting it to be "public" as it was updated by the init-method before.

这实际上是否意味着我没有任何可以处理 public 属性的方法?然后，这种模式下的 public 属性毫无意义，对吧?我也尝试过运气不佳(小提琴):

Does this actually mean, that I can't have any methods, that handle public properties? Then public properties in this pattern make little sense, right? I also tried this without luck (fiddle):

return {
    _pubic : _public,
    init2 : function() {
        _public = 'public';
    }
}

---

最后但并非最不重要的一点是，我对整个return陈述有疑问.为什么不能仅使用return this;公开所有内容?因为this应该是自调用函数的上下文，所以它不应该只是在其中返回eveyrthing吗?为什么我必须创建另一个返回的对象?在此小提琴中，它返回window对象.

---

Last, but not least, I have a question regarding the whole return statement. Why isn't it possible to just use return this; to make everything public? As this should be the context of the self-invoked function, shouldn't it just return eveyrthing in it? Why do I have to create another object, that is returned? In this fiddle it returns the window object.

推荐答案

这实际上是否意味着我没有任何处理公共属性的方法?

Does this actually mean, that I can't have any methods, that handle public properties?

否，这意味着您不能拥有公共的变量. var _public是一个变量，不能从外部访问，并且在修改私有变量时，这不会反映在您的公共._public属性中.

No, it means that you cannot have public variables. var _public is a variable, and it is not accessible from outside, and when you modify the private variable this will not be reflected in your public ._public property.

如果您想公开发布内容，请使用属性:

If you want to make things public, use properties:

var a = function() {
    var _private = null;
    function init() {
        _private = 'private';
        this._public = 'public';
    }
    function getPrivate() {
        return _private;
    }
    return {
        _public : null,
        init : init,
        getPrivate : getPrivate,
    }
}();

我可以操纵该公共财产，例如a._public ='public';.但是我无法在对象内部进行更改.

I can manipulate that public property, like a._public = 'public';. But I can't change it from within my object.

您可以在对象的方法中使用this，如上所示.或者，您可以使用a引用该对象，或者甚至可以存储对您返回的对象的本地引用.有关差异，请参见此处.

You can use this in the methods of your object, as shown above. Or you use a to reference the object, or possibly even store a local reference to the object you return. See here for the differences.

或者至少这些更改没有通过

Or at least those changes aren't passed through

是的，因为变量与属性不同(与Java等其他语言不同，全局语言除外).在对象文字中导出public: _public时，它仅从_public变量中获取当前值，并在该对象上创建一个属性.没有对变量的持久引用，对一个变量的更改也未反映在另一个变量中.

Yes, because variables are different from properties (unlike in some other languages like Java, and with exceptions for global ones). When you export public: _public in your object literal, it takes only the current value from the _public variable and creates a property on the object with it. There is no persistent reference to the variable, and changes to one are not reflected in the other.

为什么不能仅使用return this;公开所有内容?因为这应该是自调用函数的上下文，所以它不应该只是在其中返回eveyrthing吗?

Why isn't it possible to just use return this; to make everything public? As this should be the context of the self-invoked function, shouldn't it just return eveyrthing in it?

变量是JavaScript中作用域的一部分. (除了全局范围之外)这些范围不是该语言可访问的对象.

Variables are part of a scope in JavaScript. (Except for the global one) those scopes are not objects accessible to the language.

this关键字不涉及该功能的范围，而是涉及调用提供的上下文.可以是方法调用中的基本引用，也可以是构造函数调用中的新实例，或者像您的基本函数调用(或处于松散模式下的全局window对象)中的任何内容一样.

The this keyword does not refer to this scope of the function, but to the context that was provided by the call. That can be the base reference in a method call, the new instance in a constructor invocation, or just nothing in a basic function call like yours (or the global window object in loose mode).

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