We have been trying for the last two weeks to get a reliable solution to try and sync our app data with a server in the background. We have tried the Background fetch mechanism but due to the iOS restrictions on when it runs it is not a viable solution.
iOS does provide Remote Notifications (https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/pushing_background_updates_to_your_app?language=objc) that we would like to use as we can use the same mechanism on Android.
The issues is that when sending a type 2 notification CN1 only delivers the notification when the app is brought to the foreground by the user.
On Android I see there is a Build Hint for android.background_push_handling that allows the notifications to be sent to the app even if it is in the background.
Is there a similar build hint that we can use for iOS?
If not, is there a way then to override the application:didReceiveRemoteNotification:fetchCompletionHandler: method that fires when the Notification arrives so that we can forward it to our app?
You can use silent push notifications for that purpose. To send a silent push notification you just have to include "content-available" : 1" into the body of the notification. More info on that here: Apple docs-silent push notifications
You should bear in mind that this will only work when your app is in the background, it won't work when the app is killed. When the app is killed the only solution is standard push notifications, unless your app has VoIP functionality, in which case you are allowed to use PushKit framework (if you use it in an app without VoIP functionality, you won't get pass the AppStore).