EXT3.4 TreeGrid 列的格式化

{header : _('defectDensity') + '(KLOC)', dataIndex : 'defectDensity', align : 'center', width : 120,
         tpl: new Ext.XTemplate('{defectDensity:this.doFormat}', {doFormat :
                function(v, json) {
                var defect_count = json.defect_count;
                var total_change_loc = json.total_change_loc / 1000;
                    if(total_change_loc == 0){
                    return 0;
                    }else{
                    return Math.round(defect_count / total_change_loc * 100) / 100;
                    }
                }
            })
         }