swift - 我关闭Onboarding并再次运行应用程序时出现AppDelegate问题

我使用UIPageViewController启用了它的工作，但是当我第二次运行该应用程序时，Xib无法正常工作

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

        //////OnBoarding
        let lunchbefor = UserDefaults.standard.bool(forKey: "haslunched")
        self.window = UIWindow(frame: UIScreen.main.bounds)
        let lunchstoryboard = UIStoryboard(name: "onboarding", bundle: nil)
        let mainstoryboard = UIStoryboard(name: "Main", bundle: nil)

        var vc: UIViewController
        if lunchbefor{
            window?.rootViewController = MainVC()
            vc = mainstoryboard.instantiateInitialViewController()!

        }else{
            vc = lunchstoryboard.instantiateViewController(withIdentifier: "start")
        }
        UserDefaults.standard.set(true, forKey: "haslunched")
        if lunchbefor == false{

            self.window?.rootViewController = vc
            self.window?.makeKeyAndVisible()
        }else{
            window?.makeKeyAndVisible()
            window?.rootViewController = MainVC()

        }

        return true
    }

错误：


  线程1：致命错误：展开一个可选值时意外发现nil“


在这条线上：

vc = mainstoryboard.instantiateInitialViewController()!

最佳答案

我找到答案
我这样做：

  var vc: UIViewController

    if lunchbefor{
        window?.rootViewController = MainVC()
       // vc = mainstoryboard.instantiateInitialViewController()!
        vc =  MainVC()

    }else{
        vc = lunchstoryboard.instantiateViewController(withIdentifier: "start")
    }

关于swift - 我关闭Onboarding并再次运行应用程序时出现AppDelegate问题，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/59389688/