title: ExtJS6: Passing entire object or 2 fields in gridpanel's columns
body: <p>While building GridPanel's column values I need to lookup for a field if that field does not have a value, it should look for another field and render it as a column value. Now as per <a href="http://docs.sencha.com/extjs/6.0.1-classic/Ext.grid.column.Column.html#cfg-dataIndex" rel="nofollow">ExtJS6 docs</a>, we could pass a single data attribute to <code>dataIndex</code> and mould value via rendered function. But there is no mention how one can use fallback attribute if mentioned field does not have a value.</p>
  
  <p>Here is snippet:</p>
  
  <pre><code>{
    text: 'Title',
    flex: 1,
    dataIndex: '&lt;how-to-pass-object-itself-or-two-fields&gt;',
    renderer: function(value, metaData) {
      return '&lt;i class="fa fa-bars"&gt;&lt;/i&gt;' +  value;
    }
  }
  </code></pre>