我在AppDelegate.swift上使用以下代码来检查用户是否登录以更改默认ViewController。ifletuser=PFUser.currentUser()!["username"]{print("asldkeu\(user)")//Codetoexecuteifuserisloggedinletstoryboard=UIStoryboard(name:"Main",bundle:nil)letviewController=storyboard.instantiateViewControllerWithIdentifier("MainViewController")sel