javascript - Backbonejs - 在集合中，我们如何从初始化函数访问 this.var？

Question

我想要完成的是将这个帖子模型 ID 传递给一个集合，以便我可以用与其关联的其他模型填充这个特定的帖子 ID。例如:在博客文章中，包含一堆评论。我只想显示那些指向此博客文章的评论。

我一定错过了一些基本的东西。

下面是我的帖子模型，我正在实例化一个新的 CommentCollection 并传递模型和选项参数。

var PostModel = Backbone.Model.extend({
  initialize: function() {
    /*
     * we are connecting Comments collection
     * to each post item by passing along post id
     * */
    this.comments = new CommentsCollection([], { id: this.id });
  },
  defaults: {
    title: 'title here',
    body: 'body here'
  },
  urlRoot: localserver + "/posts"
});

以下是我的评论集。 console.log(this.id); 返回未定义。

var CommentsCollection = Backbone.Collection.extend({
  initialize: function(models, options) {
    this.id = options.id;
    console.log(this.id);
    return this;
  },
  url: function() {
    console.log(this.id);
    return localserver + "/posts/" + this.id + "/comments";
  },
  model: CommentModel
});

我的控制台返回以下内容:

Uncaught TypeError: Cannot read property 'id' of undefined
3

Answer 1

试试这个代码:

var CommentModel = Backbone.Model.extend({});

var CommentsCollection = Backbone.Collection.extend({
  model: CommentModel,
  initialize: function(models, options) {
    this.id = options.id;
    if(typeof this.id === 'undefined') { return; }
    this.url();
  },
  url: function() {
    var localserver = "localhost";
    console.log('from comment url: ', this.id);

    return localserver + "/" + this.id + "/comments";                  
  }
});


var PostModel = Backbone.Model.extend({
  urlRoot: "http://jsonplaceholder.typicode.com" + "/posts",
  initialize: function(option) {
    this.comments = new CommentsCollection([], { id: option.id });
  }
});

//var pm = new PostModel();
//pm.comments.fetch();
//console.log('from pm: ', pm.comments.url());

var PostsCollection = Backbone.Collection.extend({
  model: PostModel, 
  url: "http://jsonplaceholder.typicode.com" + "/posts?_sort=views&_order=DESC",
  initialize: function() {
    this.on('reset', this.getComments, this);
  },
  getComments: function() {
    this.each(function(post) {
      post.comments = new CommentsCollection([], { post: post });
      post.comments.fetch();
    });
  }
});

var pc = new PostsCollection();
pc.fetch();

我所做的是使用PostModal的选项参数。下面是代码。

var PostModel = Backbone.Model.extend({
  urlRoot: "http://jsonplaceholder.typicode.com" + "/posts",
  initialize: function(option) {
    this.comments = new CommentsCollection([], { id: option.id });
  }
});