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iosswiftpush-notificationapple-push-notificationsappdelegate

iOS push notifications and AppDelegate methods behaviour

I did some research on lots of stackoverflow issues and websites in trying to figure out how do the iOS push notifications influence AppDelegate lifecycle methods and when is which method (not) getting triggered. Main focus of the research was on "standard" iOS push notifications (with alert field) and silent ones (with just content-available set to 1) and on AppDelegate's application:didReceiveRemoteNotification and application:didFinishLaunchingWithOptions methods.

I don't want to ask lots of questions for different scenarios, but would rather try to write down the statements about different test cases I tried and ask you after that:

Is there any statement that is wrong and if yes, which one and why?

Scenario 1: App has been used and put to background by tapping the home button.

  1. If standard push notification is sent, in the moment of push notification arrival, none of the methods gets triggered, app remains inactive in background. Once push notification has been tapped and app got opened because of it, application:didReceiveRemoteNotification method got called and application:didFinishLaunchingWithOptions doesn't get called. I tested this scenario right after putting the app to background and also after an app being in background for more than an hour - same behaviour. I guess that if for some reason iOS decided to kill my app while being in background, this test case becomes like Scenario 2, statement 1 from below, right?

  2. If silent push notification is sent, in the moment of the push notification arrival, application:didReceiveRemoteNotification method got called and application:didFinishLaunchingWithOptions doesn't get called.

Scenario 2: App has been used and killed by swiping it out of the list of running apps.

  1. If standard push notification is sent, in the moment of push notification arrival, none of the methods get triggered, app remains killed. Once push notification has been tapped and app got opened because of it, application:didReceiveRemoteNotification method got called and application:didFinishLaunchingWithOptions doesn't get called.

  2. If silent push notification is sent, none of the methods gets triggered since silent push notifications fail to be sent to the app that got killed. After opening an app after notification is sent, application:didFinishLaunchingWithOptions gets called as part of the normal flow and without any push notification information. application:didReceiveRemoteNotification doesn't get called.

If you can maybe think of some other real life scenarios that I maybe forgot to mention, I would be really grateful to find out about them and what happens in those cases.

Cheers

Update #1

Thanks to Sandeep Bhandari for the update and additional scenarios. I forgot to mention in my original question that I was exploring scenarios in which application is arriving to the app that is currently not in the foreground for whatever reason.

Adding Sandeep's scenarios to the list:

Scenario 3: App is being used and push notification arrives.

  1. If standard push notification is sent application:didReceiveRemoteNotification method will get called. application:didFinishLaunchingWithOptions will not get called.

  2. If silent push notification is sent application:didReceiveRemoteNotification method will get called. application:didFinishLaunchingWithOptions will not get called.

Scenario 4: App being alive in background.

  1. If standard push notification is sent application:didReceiveRemoteNotification method will get called. application:didFinishLaunchingWithOptions will not get called.

  2. If silent push notification is sent application:didReceiveRemoteNotification method will get called. application:didFinishLaunchingWithOptions will not get called.

Solution

  • From an experience and digging alot on the iOS push notification. App being in foreground or alive in background. both situations triggers same delegate methods. only didReceiveRemoteNotification.

    The silent push notification have a different handler: (content-available 1 means silent notification)

    func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {

    }

    When app is dead. didReceiveRemoteNotification never called for regular push notification. It must be handled in didFinishLaunchingWithOptions as following:

    // handle notification when app is closed.
let notification = launchOptions?[.remoteNotification]
if notification != nil {
    self.application(application, didReceiveRemoteNotification: notification as! [AnyHashable : Any])
}

    Additional information:

    To test receiving push notification when app is killed. remove from the list that appears when double tapping home button?

    The proper way to see the logging and do debugging is by editting the run scheme and selecting Wait for executable to be launched:

    enter image description here

    Run the app from the xcode. Then send push notification from server and then tap the notification from notification center.