构造函数内部的构造函数 - 糟糕的做法？

问题描述

我正在探索一些代码，我看到了将一个构造函数嵌入到另一个构造函数中的做法多次使用：

I'm exploring some code and I saw the practice of embedding one constructor function into another used many times:

/**
 * @constructor
 */
function contact_duplicates_manager(global_objects)
{
    this.field_processors =
    {
        "Phone1Number": new phone_processor(),
        "Phone2Number": new phone_processor(),
        "Phone3Number": new phone_processor()
    }
    //...here some other code

    /**
     * @constructor
     */
    function phone_processor()
    {
        //...here some other code

        function clear_phone(phone)
        {
            //...here some code
        }
        this.is_equals = function (value1, value2)
        {
            return is_equals(clear_phone(value1), clear_phone(value2));
        }
    }
}

//... later in the code
var valid = this.field_processors[fld_name]["is_equals"](native_value, custom_value)

您认为 phone_processor 构造函数应该在 contact_duplicates_manager 之外？

Do you think phone_processor constructor function should be outside contact_duplicates_manager?

推荐答案

是的。虽然有效和有效，但它效率低，可能不可读。通过嵌套，每个 contact_duplicates_manager 实例都具有 phone_processor s，具有不同的构造函数并继承自不同的原型对象。这可能是构造函数工厂或类似模式所必需的，但这些非常罕见，我怀疑你需要它。

Yes. While being valid and working, it's not efficient and possibly unreadable. With the nesting, every contact_duplicates_manager instance has phone_processors with different constructors and inheriting from a different prototype object. This might be necessary for constructor factories or similar patterns, but those are very rare and I doubt you need it here.

我的经验法则：

最后一条规则的示例：

function Item(…) {…}
function Store {
    var that = this;
    this.items = [];
    this.addItem = function(…) {
        that.items.push(new LocalItem(…));
    };
    function LocalItem(…) {
        Item.call(this, …);
        this.store = that;
    }
    LocalItem.prototype = Item.prototype;
}

您不一定需要全局 Item 你调用类似继承的函数，有时是一个全局 proto 对象，你可以将它赋给 LocalConstructor.prototype 就够了。

You don't necessarily need the global Item function which you call inheritance-like, sometimes a single global proto object which you can assign to LocalConstructor.prototype is enough.

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