title: Listen to a specific attribute changes in a model in a nested collection in Backbone
body: <p>I have the following backbone structure:</p>
  
  <pre><code>- collection[order_items]
     - collection[menu_items]
          - price
          - quantity
  </code></pre>
  
  <p>and I want to listen for any changes in the quantity attribute, I got it working by</p>
  
  <pre><code>var CheckoutView = Backbone.Marionette.ItemView.extend({
  
      template: '#template-checkout',
  
      initialize: function (options) {
          this.order_collection = options.collection;
          _(this.order_collection.models).each(function (element, index, list) {
              this.listenTo(element.get("menu_items"), "change:quantity", this.onOrderItemsChanged);
          }, this);
  
      },
  
      onOrderItemsChanged: function (model, val, options) {
          console.log(model.get("name"));
      }
  
  });
  </code></pre>
  
  <p>But does marionette or backbone have a better way of doing it, instead of looping throught the parent collection and adding the listener to each child collection, maybe something like </p>
  
  <p><code>this.listenTo(this.order_collection, "change:menu_items:quantity", this.on OrderItemsChanged)</code></p>
  
  <p>(which didnt work for me)</p>