UIWindow Alert

alert.swift

func showAlert(message: String) {
    let alert = UIAlertController(title: "Link", message: message, preferredStyle: .alert)
    alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { action in
        switch action.style{
        case .default:
            print("default")
            
        case .cancel:
            print("cancel")
            
        case .destructive:
            print("destructive")
        }}))
    
    let topWindow = UIWindow(frame: UIScreen.main.bounds)
    topWindow.rootViewController = UIViewController()
    topWindow.windowLevel = UIWindow.Level.alert + 1
    topWindow.makeKeyAndVisible()
    topWindow.rootViewController?.present(alert, animated: true, completion: nil)
}