Displaying a stock iOS notification banner when your app is open and in the foreground?

iOS 10 adds the UNUserNotificationCenterDelegate protocol for handling notifications while your app is in the foreground.

The UNUserNotificationCenterDelegate protocol defines methods for receiving notifications and for handling actions. When your app is in the foreground, arriving notifications are delivered to your delegate object instead of displayed automatically using the system interfaces.

Swift:

optional func userNotificationCenter(_ center: UNUserNotificationCenter, 
                     willPresent notification: UNNotification, 
      withCompletionHandler completionHandler: (UNNotificationPresentationOptions) -> Void)

Objective-C:

- (void)userNotificationCenter:(UNUserNotificationCenter *)center 
       willPresentNotification:(UNNotification *)notification 
         withCompletionHandler:(void (^)(UNNotificationPresentationOptions options))completionHandler;

The UNNotificationPresentationOptions flags allow you to specify UNNotificationPresentationOptionAlert to display an alert using the text provided by the notification.

This is key as it allows you to display the alert while your app is open and in the foreground, which is new for iOS 10.

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Sample code:

class AppDelegate: UIResponder, UIApplicationDelegate {
    
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        
        // Set UNUserNotificationCenterDelegate
        UNUserNotificationCenter.current().delegate = self
        
        return true
    }
    
}

// Conform to UNUserNotificationCenterDelegate
extension AppDelegate: UNUserNotificationCenterDelegate {
    
    func userNotificationCenter(_ center: UNUserNotificationCenter,
           willPresent notification: UNNotification,
           withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void)
    {
        completionHandler(.alert)
    }
    
}