How to get iCloud Notifications for Extra functions?

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Created Apr ’20

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For the past two days I've been trying to figure out how to get the notification when the iCloud data has changed. I use a NSPersistentCloudKitContainer and am able to see my changes from one device in another. I just added local notifications to my app and I save the notification to an iCloud entity whenever a user sets it.

Since I'm adding this notification in iCloud, a remote notification with iCloud changes will be sent to the users devices with iCloud enabled. What I would like to do is when the device gets this notification, read from the new data and set a local notification on the current device if a notification entity is found.

But I can not seem to figure out how to intercept this change notification. I tried using didReceive and didReceiveRemoteNotification from the AppDelegate, but none of these functions fired when the device received the iCloud changes. In the Xcode console I can see that the device is notified with the data.

How can I intercept the background notification that contains the new data so I can add a local notification on the device?

Here is how I set up my iCloud container:

class CoreDataManager {
    static let sharedManager = CoreDataManager()
    private init() {}


    //setting the persistentContainer
    lazy var persistentContainer: NSPersistentContainer = {


        //get local or iCloud container if user wants to use iCloud
        var useCloudSync = UserDefaults.standard.bool(forKey: "useCloudSync")


        let containerToUse: NSPersistentContainer?
        if useCloudSync {
           containerToUse = NSPersistentCloudKitContainer(name: "App")
        } else {
            containerToUse = NSPersistentContainer(name: "App")
            let description = containerToUse!.persistentStoreDescriptions.first
            description?.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
      }


      // Enable history tracking and remote notifications
        guard let container = containerToUse, let description = container.persistentStoreDescriptions.first else {
            fatalError("Hey Listen! ###\(#function): Failed to retrieve a persistent store description.")
        }
        description.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
       
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {              
                fatalError("Hey Listen! Unresolved error \(error), \(error.userInfo)")
            }
        })
       
        container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
        container.viewContext.transactionAuthor = appTransactionAuthorName       
        container.viewContext.automaticallyMergesChangesFromParent = true
        do {
            try container.viewContext.setQueryGenerationFrom(.current)
        } catch {
            fatalError("Hey Listen! ###\(#function): Failed to pin viewContext to the current generation:\(error)")
        }
       
        // This notification never gets called
        NotificationCenter.default.addObserver(
            self, selector: #selector(type(of: self).storeRemoteChange(_:)),
            name: .NSPersistentStoreRemoteChange, object: container)
       
        return container
    }()

You can think of this as a user setting a reminder in the Apple reminders app and how that notification pops up on all of my iCloud devices at the time I set it at.

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