В iOS12 shouldAlwaysAlertWhileAppIsForeground keyPath удален и больше не поддерживается.
Чтобы добиться этого на iOS12:
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
UNUserNotificationCenter.current().delegate = self
...
}
...
extension AppDelegate: UNUserNotificationCenterDelegate {
// The method will be called on the delegate only if the application is in the foreground.
// If the method is not implemented or the handler is not called in a timely manner then the notification will not be presented.
// The application can choose to have the notification presented as a sound, badge, alert and/or in the notification list.
//This decision should be based on whether the information in the notification is otherwise visible to the user.
func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
completionHandler([.alert, .sound])// Will present an alert and will play a sound when a notification arrives
}
}