public function actionUp($id)
    {
        if ($category = Category::findOne($id)) {
            $this->trigger(self::EVENT_BEFORE_EDIT_CATEGORY);

            if ($category->movePrev()) {
                $this->trigger(self::EVENT_AFTER_EDIT_CATEGORY,
                    new CategoryEvent(['id' => $id]));
                if (\Yii::$app->request->isAjax) {
                    return 'up';
                }
            }
            return $this->actionIndex();
        }
        throw new NotFoundHttpException();
    }