添加注释

app/Http/Controllers/UserExchangesController.php

@@ -55,6 +55,7 @@ class UserExchangesController extends Controller
      */
     public function exchange(Request $request, UserExchangeService $service)
     {
+        //这个是兑换的商品id,不是兑换流水的id,因为这个时候还没有生成
         $exchangeId = $request->get('exchange_id');
         //先写死用于测试
         $exchangeId = 1;