/**
  * Executes the execute method of an action.
  *
  * @param sfAction $actionInstance An sfAction instance
  *
  * @return string The view type
  */
 protected function executeAction($actionInstance)
 {
     // execute the action
     $actionInstance->preExecute();
     $viewName = $actionInstance->execute($this->context->getRequest());
     $actionInstance->postExecute();
     return null === $viewName ? sfView::SUCCESS : $viewName;
 }