EXTJS 4 Json nested data in grid panel

{  "success":true,  "error":false,  "redirectUrl":null,  "fund":[{    "cat_id":1,    "catname":"Europe OE Japan Large-Cap Equity",    "region":{      "region_id":2,      "region_name":"JAPAN"    }    },{    "cat_id":2,    "catname":"Europe OE Europe Large-Cap Growth Equity",    "region":{      "region_id":1,      "region_name":"EUROPE"    }   }]
} 
Ext.define('Fund', {    extend: 'Ext.data.Model',    fields: [      { name: 'catname',     type: 'string' },           { name: 'cat_id',      type: 'int' },      { name: 'region_name', type: 'string',          mapping: 'region.region_name'},      { name: 'region_id',   type: 'int',          mapping: 'region.region_id'}         ]   });  

copy from http://stackoverflow.com/questions/11562604/extjs-4-json-nested-data-in-grid-panel