title: How to get value from Ext.data.Store ?
body: <p>this is my code</p>
  
  <pre><code>var store = {
      user_store: new Ext.data.Store({
          autoLoad: false,
          proxy: new Ext.data.HttpProxy({
              url: 'a/b/c',
          }),
          remoteSort: true,
          baseParams: {
  
          },
          reader: new Ext.data.JsonReader({
              totalProperty: 'total',
              root: 'root',
              fields: ['roles']
          })
      })
  };
  store.user_store.load();​
  </code></pre>
  
  <p>this is my json </p>
  
  <pre><code>{"roles":"2"}
  </code></pre>
  
  <p>I wnat to ask. How do I get the roles's value is "2".</p>
  
  <p>(PS:Sorry,my English is not very well.)</p>