Ext 表格列中按钮权限设置

getClass:function(v ,metadata ,record ,rowIndex ,colIndex ,store ){
 var dutyStage = STORE.getAt(rowIndex).get('XXX')；//获取表格列
   var flag = false;
   Ext.Ajax.request({
      url:‘action.do',
      method:'POST',
      async:false,
      success:function(response){
         var text = response.responseText;
         if(text == "true"){
            flag = true;
         }
      }
   })
   if(flag){
      return 'x-hidden';
   }
}