title: autocomplete combobox extjs with remote ajax store
body: <p>I want to add a combobox in my app with a remote store. I have a store that call a php script that returns data in json format and I linked it with my combobox.
  The store is autoLoaded but my combobox is still empty.
  Here's my store</p>
  
  <pre><code>// Define autocomplete model
  Ext.define('modelloAC', {
      extend: 'Ext.data.Model',
      fields: [
          { name: 'telaio' }
      ]
  });
  // store auto complete
  var autoCompleteStore = Ext.create('Ext.data.Store', {
      model: modelloAC,
      autoLoad: true,
      proxy: {
          type: 'ajax',
          url: 'script/request.php?operazione=gettelai',
          reader: {
              type: 'json',
              root: 'telai',
              totalProperty: 'results'
          }
      }
  });
  </code></pre>
  
  <p>My PHP return a JSON array:</p>
  
  <pre><code>{"results":207,"telai":[{"telaio":"ZAR93200001271042"},{"telaio":"ZLA84000001738127"},{"telaio":"VF3WC9HXC33751301"},{"telaio":"W0L0AHL3555247737"}]}
  </code></pre>
  
  <p>My combobox:</p>
  
  <pre><code>    xtype: 'combo',
      name: 'telaio',
     //hideTrigger: true,
     store: autoCompleteStore,
     typeAhead: true,
     queryMode: 'remote',
     fieldLabel: 'Telaio'
  </code></pre>
  
  <p>My store loads perfectly but my combobox is empty, where's the problem?</p>