private function build_ajax_request(AjaxRequest $request, array $fields, $condition)
 {
     if (is_array($fields)) {
         foreach ($fields as $field) {
             $request->add_param($field->get_id(), '$FF(\'' . $field->get_id() . '\').getValue()');
         }
     }
     if (!empty($condition)) {
         return 'if (' . $condition . '){' . $request->render() . '}';
     }
     return $request->render();
 }