title: How to get handle to a cell field in Extjs Grid
body: <p>The data for the grid looks something like this:</p>
  
  <pre><code>data: [{
      field1: abc
      field2: [
          {value: 0, label: Blue}, 
          {value: 1, label: Green}
      ]
  },
  {
      field1: def
      field2: [
          {value: 0, label: Red}, 
          {value: 1, label: Pink}
      ]
  }]
  </code></pre>
  
  <hr>
  
  <p>grid component config looks something like:</p>
  
  <pre><code>{
  xtype: 'grid',
  ....
      columns: [
          {
              dataIndex: field1
          },
          {
              dataIndex: field2
              editor: {
                  xtype: combobox,
                  displayField: label,
                  valueField: value,
                  store: new someSampleStore();
              }
          }
      ]
  }
  </code></pre>
  
  <p>Now, the grid's column #2 has a combobox.
  For Grid's row 0, column 1; combobox dropdown should display these options: Blue, Green
  For Grid's row 1, column 1; combobox dropdown should display these options: Red, Pink</p>
  
  <p>Do I need to manually load the data into each combobox (each row) or is there any way I can specify config in column definition so that the combobox picks up data for 'field2' ?</p>