public function actionCreate()
 {
     if ($carousel = Yii::$app->request->post()) {
         $model = new Carousel();
         $files = Fileupload::upload();
         $carousel['img'] = isset($files[0]) ? $files[0] : './img/default.jpg';
         $model->set_carousel_data($carousel);
         if ($model->save(false)) {
             return $this->render('create', ['msg' => '添加轮播图成功!']);
         } else {
             return $this->render('create', ['msg' => '添加轮播图失败,请刷新重试!']);
         }
     } else {
         return $this->render('create');
     }
 }