title: Backbone.js Collection model value not used
body: <p>Backbone is not using the model specified for the collection. I must be missing something.</p>
  
  <pre><code>App.Models.Folder = Backbone.Model.extend({
    initialize: function() {
      _.extend(this, Backbone.Events);
  
      this.url = "/folders";
      this.items = new App.Collections.FolderItems();
      this.items.url = '/folders/' + this.id + '/items';
    },
  
    get_item: function(id) {
      return this.items.get(id);
    }
  });
  
  App.Collections.FolderItems = Backbone.Collection.extend({
    model: App.Models.FolderItem
  });
  
  App.Models.FolderItem = Backbone.Model.extend({
    initialize: function() {
      console.log("FOLDER ITEM INIT");
    }
  });
  
  
  var folder = new App.Models.Folder({id:id})
  folder.fetch();
  
  // later on change event in a view
  folder.items.fetch();
  </code></pre>
  
  <p>The folder is loaded, the items are then loaded, but they are not FolderItem objects and FOLDER ITEM INIT is never called. They are basic Model objects.</p>
  
  <p>What did I miss? Should I do this differently?</p>
  
  <p><strong>EDIT:</strong>
  Not sure why this works vs the documentation, but the following works. Backbone 5.3</p>
  
  <pre><code>App.Collections.FolderItems = Backbone.Collection.extend({
    model: function(attributes) {
      return new App.Models.FolderItem(attributes);
    } 
  });
  </code></pre>