Question

在我正在创建的对象的init函数中，我想创建另一个对象的新实例。

目前，我的初始化代码如下所示：

    var myObj = {

getData: function(){

      var instance = this;

      // Display preloader gif
      instance.selectors.preloader.fadeIn();

      // Make call for appropriate data */
      dataManager.feed.get( function(data){

        for( var i = 0, len = data.feed.length; i < len; i++ ){

          var template = '';

        }
      }, window, null, '' );

      instance.displayVideos();

    },

    init: function(){

          var instance = this;

          // Create new DataManager object
          var dataManager = new DataManager();
    }



    }

myObj.init（）;

我的问题是我收到错误告诉我DataManager没有定义，有人能解释我是如何引用这个对象的吗？

Answer 1

看，你的代码可能是可以挽救的，但维护起来会很糟糕。因此，我建议您使用一个闭包，在最终曝光之前，您可以根据需要准备您的对象：

var myObj = (function(current)
{
    'use strict';//<-- not necessary, but highly recommended
    var instance = {};//<-- this is going to become the value myObj references
    //if you want the init method, make a function object
    var init = function()
    {
        instance.dataManager = new DataManager();
    };
    instance.init = init;//<-- make it "public"
    //alternatively:
    instance.dataManager = new DataManager();
    //OR to have access to an instance of the DataManager object, but as a 
    // "private" property:
    var dataManager = new DataManager();
    //All methods or functions declared in this scope will have access to this object, 
    // the outer scope won't!
    //same for getData, use either one of the following:
    var getData = function()
    {
        //refer to the instance, not by using this, but use instance var
        //which is safer, and immutable thanks to the closure we're building
    };
    instance.getData = getData;
    //OR:
    instance.getData = function()
    {
        //same function body, just created and assigned directly
    };
    //if you chose to use the init method:
    instance.init();
    //if you created an init function, but didn't assign it to the instance object:
    init();
    //when the instance object is all set up and good to go:
    return instance;//will be assigned to the myObj variable
}(this));//call function and pass current scope as argument

然后，只有这段代码我真的没有得到：

dataManager.feed.get( function(data)
{
    //...
    for( var i = 0, len = data.feed.length; i < len; i++ )
    {//loop through an array of sorts
         var template = '';//and initialize a variable to an empty string each time?
    }
}, window, null, '' );

为什么呢？重点是什么，或者这只是一个虚拟循环？

我看到它的方式，这里有两个主要问题。第一个是您未能包含DataManager构造函数。假设您的代码中定义了构造函数：

var myObj = {
    init: function()
    {
        var instance = this;
        // Create new DataManager object
        var dataManager = new DataManager();
    },
    myObj.init();//<== this can't work
};

在您仍在定义时，您正在调用对象文字的方法。这不起作用：

var myObj = { init: function() { var instance = this; // Create new DataManager object var dataManager = new DataManager(); } }; myObj.init();//<== now myObj exists, and has an init method

Answer 2

应在调用init（）方法之前定义DataManager对象。我在你的代码中看到了另外一个问题（）。 dataManager变量未在getData（）函数中声明/赋值。在这种情况下使用对象级变量。试试这个：在init方法中 -

init：function（）{

      var instance = this;

      // Create new DataManager object
      this.dataManager = new DataManager();  }

并在getData（）方法中使用

this.dataManager

而不是

DATAMANAGER

使用另一个对象的init函数创建新对象

2 个答案: