我正在iOS中实现登录。我想先放松到之前的VC(IntroVC)，并显示已完成的注册提醒关于IntroVC已完成。(completingSignUp是Unwind函数。)@IBActionfunccompletingSignUp(_segue:UIStoryboardSegue){letcompletedAlert=UIAlertController(title:"Completing",message:"Congratulations.",preferredStyle:.alert)letok=UIAlertAction(title:"OK",style:.default,handl