This event occurs before data loading and allows to customize sorting of dataset

        $gridConn->event->attach("beforeSort",handlerFunc);

handlerFunc gets the following arguments:

• $sort_by - SortInterface object

Sample of usage:

   function custom_sort($sorted_by){
          // SORT BY LENGTH(some_field)
          $sorted_by->rules[0]["name"]="LENGTH(some_field)";
   }
   $conn->attach->event("beforeSort","custom_sort");