UNUserNotificationCenter didReceive not being called

Question

When I send a push notification, and the app is in the foreground willPresent is called. didReceive is never called. When the application is in the background, and a push notification is received, the alert is shown, but the application never calls didReceive, or willPresent.

In Project > Capabilities, I have Background Modes Location updates, and Remote notifications checked. Location updates is for unrelated code.

I have also enabled push notifications. This is working fine, as they are being received.

I have implemented the UNUserNotificationCenter notification stuff in my AppDelegate, see below:

import UserNotifications
...

class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterDelegate {
...

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

    // MARK: - Push Notifications

    func registerForPushNotifications(application: UIApplication) {
        let notificationCenter = UNUserNotificationCenter.current()
        notificationCenter.delegate = self
        notificationCenter.requestAuthorization(options: [.badge, .sound, .alert], completionHandler: {(granted, error) in
            if (granted)
            {
                UIApplication.shared.registerForRemoteNotifications()
            }
            else{
                //Do stuff if unsuccessful...
                print("Unsuccessful in registering for push notifications")
            }
        })
    }

    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        //convert the deviceToken to a string
        let deviceTokenString = deviceToken.map { String(format: "%02.2hhx", arguments: [$0]) }.joined()

        let ud = UserDefaults.standard
        ud.set(deviceTokenString, forKey: "deviceToken")
    }

    func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
        //Handle the notification
        print("User Info = ",notification.request.content.userInfo)
        completionHandler([.alert, .badge, .sound])
    }

    func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {
        //handle the notification
        print("Push notification: ",response.notification.request.content.userInfo)

        ... code to import the notification data into Core Data.

        completionHandler()
    }

...
}

Any ideas why didReceive is not being called?

This is the received push notification:

[AnyHashable("aps"): {
    alert = "[name] has added you as a friend.";
    category = "NEWS_CATEGORY";
    "related_user_id" = 55;
    sound = default;
    type = "friend_request";
}]

iOS 10.1, Swift 3.

Answer 1

I found that I need to set the delegate after I get the permission granted.

Otherwise when you lunch the app first time ever you register the delegate before you get the permissions and the didReceive function is not triggered - this happened only on the first time you run app, after kill and relaunch it was called just fine.

See below:

 UNUserNotificationCenter.current().requestAuthorization(options: authOptions, completionHandler: { (granted, error) in
        if granted {
            // Register after we get the permissions.
            UNUserNotificationCenter.current().delegate = self
        }
    })

Answer 2

didReceive is not executed when you receive a notification, it's executed when the user performs an action on the received notification

From the Apple documentation at https://developer.apple.com/documentation/usernotifications/unusernotificationcenterdelegate

Called to let your app know which action was selected by the user for a given notification.

Meaning this method will be called when the user performs an action on the received notification (push the notification, swipe down, etc)