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

    // notification was never shown to the user
    if UserDefaults.standard.bool(forKey: "doNotShowNotificationAgain") == false {
        NotificationManager.shared.schedule(notification)
    }


func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
         if notification.request.identifier == "remindUserToVisitScreenX" {
             UserDefaults.standard.set(true, forKey: "doNotShowNotificationAgain")
         }
}

//.. some uninteresting code


override func viewWillAppear() {
    // if user notification has never been shown, reschedule (i.e. reset) notification
    NotificationManager.shared.schedule(notification)
{