title: Extjs4 combobox displayValue in grid
body: <p>Please, help.
  I want to show my <code>displayValue</code> in the Grid.
  I found the solution <a href="https://stackoverflow.com/questions/5133453/combobox-in-editable-grid-cant-see-the-value">here</a>, but I can't understand how use it. My code:</p>
  
  <pre><code>columns:[...,{
      header: 'Product',
      id: 'combo',
      locked: true,
      dataIndex: 'prod_id',
      editor: {
          xtype: 'combobox',
          store: new Ext.data.Store({
              fields: ['value','display'],
              data: prod_list
      }),
      displayField: 'display',
      valueField: 'value'
      }
  },...]
  </code></pre>
  
  <h2>Solution</h2>
  
  <pre><code>Ext.util.Format.comboRenderer = function(combo){
      return function(value){
      var record = combo.findRecord(combo.valueField || combo.displayField, value);
          return record ? record.get(combo.displayField) : combo.valueNotFoundText;
      }
  }
  
  {
      header: 'Товар',
      id: 'combo',
      locked: true,
      dataIndex: 'prod_id',
      editor: MyEditor,
      renderer: Ext.util.Format.comboRenderer(MyEditor)
  }
  </code></pre>
  
  <p>I tried to define editor outside of the column array.</p>
  
  <pre><code>    var MyEditor = new Ext.form.field.ComboBox({
          store: new Ext.data.Store({
              fields: ['value','display'],
              data: prod_list
          }),
          displayField: 'display',
          valueField: 'value'
      });
  </code></pre>
  
  <h3>And all is fine, <strong>but I can't edit it</strong>. What is the problem?</h3>
  
  <p>Sorry for my English.</p>