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问题:

I've got a template for a todo with a list for comments. Each todo has an array "comments" of comments in localstorage. I fetch all todos, iterate through each todo's "comments" array and I want all comments to be assigned to the corresponding todo. How do I append to the right comment-list?

Currently I get the output like this one:

Post1
  Comment1_Post1
  Comment2_Post1
  Comment1_Post2
  Comment2_Post2
Post2
  Comment1_Post2
  Comment2_Post2

Edit1: the new CommentCollectionView

 render: function() {  
        this.$el.html(this.template());
        var commentList = this.$("ul.comment-list");
        this.collection.each(function(comment) {
            var commentView = new CommentView({model: comment});
            commentList.append(commentView.render().el);
        });            
        return this;
    },

HTML:

<body>
<div class="content">
   <ul class="todos-list"></ul>
</div>

// Templates
 <script type="text/template" id="todo-template">    
          <label class="todo-content"><%= content %></label>
          <ul class="comment-list" style="margin-left: 2em"></ul>
</script>

<script type="text/template" id="comment-template">    
          <label class="comment-content"><%= content %></label>      
</script>

Todo View:

var TodoView = Backbone.View.extend({
     tagName: "li",
     template: _.template($("#todo-template").html()),     
     events: {
         "click button.addComment": "addComment"      
     },    
     initialize: function() {
         _.bindAll(this, "render");        
         this.model.bind("change", this.render);        
         var commentsArray = this.model.get("comments");          
         var commentCollection = new CommentCollection();
         commentCollection.add(commentsArray); 
         var commentCollectionView = new CommentCollectionView({model: commentCollection});       
     }
  });

Comment Collection View:

 var CommentCollectionView = Backbone.View.extend({
    initialize: function() {
         _.bindAll(this, "render", "appendItem", "addAll", "renderComment");
         this.model.bind("reset", this.addAll);
         this.model.bind("change", this.render);             
         this.model.bind("add", this.appendItem);            

         this.model.trigger("reset");
    },
    addAll: function() {
         this.model.each(this.appendItem);
    },        
    appendItem: function(comment) {                    
        var commentView = new CommentView({model: comment}); 
        $("ul.comment-list").append(commentView.render().el);    
   }    
});

回答1:

The problem is in the definition of the TodoModel, you did not pasted the code of it but I could assume the issue, is a common issue with data-types that are objects.

TodoModel has an attribute that you are defining in your default in this way:

var TodoModel = Backbone.Model.extend({
  defaults : {
     //some
     comments : []
  }
});

So comments is an array that is always being used in all of your instances of TodoModel. Change your defaults to be in this way:

var TodoModel = Backbone.Model.extend({
  defaults : function(){
     return {
       //some
       comments : []
     }
  }
});

Update, because seems to be an issue with the scope of the selector of jQuery: To be sure that you use only DOM elements of your current view use this. instead of the normal jQuery Call, example: this.$('ul.comment-list')

回答2:

I think your problem is right here:

appendItem: function(comment) {                    
    var commentView = new CommentView({model: comment}); 
    $("ul.comment-list").append(commentView.render().el);    
}

Your $('ul.comment-list') finds all the <ul class="comment-list"> when you only want the specific <ul> for that todo item.

You should break your #todo-template into two pieces:

<script type="text/template" id="todo-template">    
    <label class="todo-content"><%= content %></label>
</script>
<script type="text/template" id="comments-template">
    <ul class="comment-list" style="margin-left: 2em"></ul>
</script>

Then use #comments-template as the template for CommentCollectionView:

var CommentCollectionView = Backbone.View.extend({
    template: _.template($("#comments-template").html()),
    render: function() {
        this.$el.html(this.template());
        return this;
    },
    //...
});
var TodoView = Backbone.View.extend({
    //...
    render: function() {
        this.$el.html(this.template(...));

        // Use 'collection' here, not 'model'
        var c = new CommentCollectionView({collection: commentCollection});       
        this.$el.append(c.render().el);
        return this;
    }
});

Then your appendItem becomes:

appendItem: function(comment) {                    
    var commentView = new CommentView({model: comment}); 
    this.$el.append(commentView.render().el);
}

and that should put the CommentView into the right <ul>.