UIWindow not showing over content in iOS 13

Question

I am upgrading my app to use the new UIScene patterns as defined in iOS 13, however a critical part of the app has stopped working. I have been using a UI

Answer 1

Swift 4.2 iOS 13 UIAlertController extension

This code full working in iOS 11, 12 and 13

import Foundation
import UIKit

extension UIAlertController{
    private struct AssociatedKeys {
        static var alertWindow = "alertWindow"
    }
    var alertWindow:UIWindow?{
        get{
            guard let alertWindow = objc_getAssociatedObject(self, &AssociatedKeys.alertWindow) as? UIWindow else {
                return nil
            }
            return alertWindow
        }
        set(value){
            objc_setAssociatedObject(self,&AssociatedKeys.alertWindow,value,objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
    }

    func show(animated:Bool) {
        self.alertWindow = UIWindow(frame: UIScreen.main.bounds)
        self.alertWindow?.rootViewController = UIViewController()
        self.alertWindow?.windowLevel = UIWindow.Level.alert + 1
        if #available(iOS 13, *){
            let mySceneDelegate = UIApplication.shared.connectedScenes.first?.delegate as? SceneDelegate
            mySceneDelegate!.window?.rootViewController?.present(self, animated: animated, completion: nil)
        }
        else{
            self.alertWindow?.makeKeyAndVisible()
            self.alertWindow?.rootViewController?.present(self, animated: animated, completion: nil)
        }
    }
}