title: extjs combo Box with hasone association property + editable grid
body: <p>I have a IPIdentifierMod model that has a hasone association with BaseInfo model</p>
  
  <pre><code>Ext.define('JP.model.IPIdentifierMod', {
  extend:'Ext.data.Model',
  fields:[
      'enterpriseIdType',
      {
          name: 'referenceVerifiedDate',
          type: 'date',
          convert: function(v, record) {
              return Ext.Date.format((new Date(v)), 'Y-m-d');
              console.log(v);
              console.log(record);
          }
      }
  ],associations: [
      { type: 'hasOne',
          model: 'BaseInfoMod',
          name:'enterpriseIdType'
      }
  ]
  </code></pre>
  
  <p>});</p>
  
  <p>baseInfo:</p>
  
  <pre><code>Ext.define('JP.model.BaseInfoMod', {
  extend:'Ext.data.Model',
  fields:[
      'typeId',
      'typeName',
      'parentId',
      'priority'
  ],
  proxy: {
      type: 'ajax',
      reader: {
          type: 'json',
          root:'results',
          idProperty: 'typeId'
      },
      api: {
          read : contextPath + '/baseInfo/getBaseInfo'
      },
      extraParams: {
          baseEntityNo: ''
      }
  }
  </code></pre>
  
  <p>});</p>
  
  <p>and I show IPIdentifierMod data in a grid</p>
  
  <p>corresponding grid column to show naemType of BaseInfo is:</p>
  
  <pre><code>    {
      header:'Name Type',
      dataIndex:'enterpriseIdType',
      sortable:true,
      renderer: function(value) {
          return value.typeName;
      }
  },
  </code></pre>
  
  <p>This works fine. The enterpriseIdType.typeName is displayed in the column.</p>
  
  <p>I now added a RowEditingPlugin and added the following editor to this column</p>
  
  <pre><code>        editor: {
          allowBlank: false,
          xtype: 'combobox',
          displayField: 'typeName',
          valueField: 'typeId',
          store: 'EnterpriseIdType',
      }
  </code></pre>
  
  <p>In the editor,the value of the field is "[object Object]" . 
  I need to render this object to display the name just like I did to the actual column.
  Also when I choose an item in the ComboBox, an enterpriseIdType object is not created in the data, 
  it just saves the value of the field specified in the valueField.
  I searched it and find something like my problem without any answer.
  <a href="http://www.sencha.com/forum/showthread.php?245015-using-ComboBox-on-HasOne-association-field" rel="nofollow">sencha forum</a></p>
  
  <p>thank you</p>