title: Parse nested json with a proxy in a Sencha Touch 2 store using rootProperty
body: <p>I have a JSON response that is nested like the following (simplified, but same format):</p>
  
  <pre><code>{
      "response":{
          "v":"1.0",
          "users":[
              {
              "firstName":"Nicole",
              "LastName":"A",
              },
              {
              "firstName":"John",
              "LastName":"B",
              },
              {
              "firstName":"Bob",
              "LastName":"C",
              }
          ],
      }
  }
  </code></pre>
  
  <p>Here is the model:</p>
  
  <pre><code>Ext.define('MyApp.model.User', {
      extend: 'Ext.data.Model',
  
      requires: [
          'Ext.data.Field'
      ],
  
      config: {
          fields: [
              {
                  name: 'firstName'
              },
              {
                  name: 'lastName'
              }
          ]
      }
  });
  </code></pre>
  
  <p>I am starting from the sencha architect tutorial for CityBars, so most of the code should be quite basic, and I am just trying to get the users from the json response loaded.  Here is the controller:</p>
  
  <pre><code>Ext.define('MyApp.controller.User', {
      extend: 'Ext.app.Controller',
  
      launch: function() {
                  var me = this;
                  Ext.Viewport.setMasked({ message: 'Loading Attendees...' });
                  me.getUsers(function (store) {
                  me.getDataList().setStore(store);
                });
      },
  
      getUsers: function(callback) {
              var store = Ext.data.StoreManager.lookup('UserStore'),
              url = 'http://urltogetjsonresponse'
              store.getProxy().setUrl(url);
              store.load(function() {
                              callback(store);
                            });
      },
  });
  </code></pre>
  
  <p>Here is the store:</p>
  
  <pre><code>Ext.define('MyApp.store.UserStore', {
      extend: 'Ext.data.Store',
  
      requires: [
          'MyApp.model.User',
          'Ext.data.proxy.JsonP',
          'Ext.data.reader.Json'
      ],
  
      config: {
          model: 'MyApp.model.User',
          storeId: 'UserStore',
          proxy: {
              type: 'jsonp',
              reader: {
                  type: 'json',
                  rootProperty: 'response.user'
              }
          }
      }
  });
  </code></pre>
  
  <p>I tried 'response.user' but it did not work for me. I have already looked all over and know that using rootProperty: 'user' would work, if the users attribute were at the same level as "response" instead of nested under it. I have also tried adding record: 'users' but that did not seem to work either.</p>
  
  <p>If anybody knows if this is doable and has an easy solution to this, that would be great. I don't actually understand how the proxy works, so if anybody can explain a bit about that, it would be helpful too. Thanks.</p>