use yii

biz/coupon/services/CouponAssetService.php

@@ -4,6 +4,7 @@ namespace biz\coupon\services;
 
 use biz\base\services\BaseService;
 use biz\coupon\classes\CouponAssetClass;
+use Yii;
 
 class CouponAssetService extends BaseService
 {