title: Failed to implement computed property in emberjs
body: <p>My fixture data contains multiple array.Out of this multiple array <code>cart_items</code> contains some product data.</p>
  
  <p></p>
  
  <p>I am trying to calculate total no of products available in cart data (based on length of <code>cart_items</code> items) but i am not able to calculate no of items are present in <code>cart_items</code>.</p>
  
  <p></p>
  
  <p>In router i have selected application fixture as model for current route,as follow :</p>
  
  <pre><code> Astcart.IndexRoute = Ember.Route.extend({
      model: function() {
        return Astcart.Application.find();
      }
    }); 
  </code></pre>
  
  <p></p>
  
  <p>Computed property code : </p>
  
  <pre><code>Astcart.IndexController = Ember.ArrayController.extend({
       tot_cart_prd: function() {
            return this.get("model.cart_items").get('length');
        }.property("@each.isLoaded")
  });
  </code></pre>
  
  <p>And my fixture data is :</p>
  
  <pre><code>Astcart.Application.adapter = Ember.FixtureAdapter.create();
  
  Astcart.Application.FIXTURES = [
      {
  
          "logo_url": "img/logo.jpg",
          "logged_in": {
              "logged": true,
              "username": "sachin",
              "account_id": "4214"
          },
          "category_list": [
              {
                  "id": "1",
                  "name": "Mobiles &amp; Accessories"
              },
              {
                  "id": "2",
                  "name": "Computers &amp; Software"
              },
              {
                  "id": "3",
                  "name": "Fashion"
              },
              {
                  "id": "4",
                  "name": "Electronics"
              },
              {
                  "id": "5",
                  "name": "Watches &amp; Jewelry"
              },
              {
                  "id": "6",
                  "name": "Health &amp; Beauty"
              },
              {
                  "id": "7",
                  "name": "Games"
              },
              {
                  "id": "8",
                  "name": "Books &amp; Entertainment"
              },
              {
                  "id": "9",
                  "name": "Gaming"
              },
              {
                  "id": "10",
                  "name": "Shoes &amp; Bags"
              }
          ],
          "cart_items": [
              {
                  "id": "1",
                  "name": "Samsung Galaxy Tab 2",
                  "qty": "1",
                  "price": "1245.12",
                  "subtotal": "7842.23"
              },
              {
                  "id": "2",
                  "name": "Samsung Galaxy Tab 2",
                  "qty": "1",
                  "price": "1245.12",
                  "subtotal": "7842.23"
              },
              {
                  "id": "3",
                  "name": "Samsung Galaxy Tab 2",
                  "qty": "1",
                  "price": "1245.12",
                  "subtotal": "7842.23"
              }
          ]           
      }
  ];
  </code></pre>
  
  <p>I have posted my code <a href="http://jsfiddle.net/sachin1989/8SEvk/1/" rel="nofollow">here(JSFiddle)</a>.</p>
  
  <p>Can any one tell me why <code>this.get("model.cart_items")</code> is returning null?</p>