Migrating Data to App Groups Disables iCloud Syncing

Question

I am adding a Today Extension to my existing app. I have added the an App Group and used this post to successfully migrate my Core Data's data to the App Group's store. My app uses both a NSPersistentCloudKitContainer (when iCloud is toggled on) and a NSPersistentContainer (iCloud toggled off). While the data in both containers migrate successfully, I am no longer able to sync between my devices when using NSPersistentCloudKitContainer. In the console I get these two errors:

CoreData: error: CoreData+CloudKit: -[NSCloudKitMirroringDelegate _performSetupRequest:]_block_invoke(837): : Failed to set up CloudKit integration for store: (URL: file://path/name.sqlite)

Error Domain=NSCocoaErrorDomain Code=134060 "A Core Data error occurred." UserInfo={NSLocalizedFailureReason=The mirroring delegate could not initialize because it's store was removed from the coordinator.}

The path from the first error message is the path of the oldURL before switching to App Groups. So I believe I just need to tell iCloud to not try to integrate CloudKit at that store location and use the App Group's store location.

But I can not figure out how to do this. Can anyone help?

Core Data code:

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

    lazy var persistentContainer: NSPersistentContainer = {
        var useCloudSync = UserDefaults.standard.bool(forKey: "useCloudSync")

        //Get the correct container
        let containerToUse: NSPersistentContainer?
        if useCloudSync {
           containerToUse = NSPersistentCloudKitContainer(name: "App")
        } else {
            containerToUse = NSPersistentContainer(name: "App")      
        }

        guard let container = containerToUse else {
            fatalError("Couldn't get a container")
        }

        //Set the storeDescription
        let storeURL = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: "group.App")!.appendingPathComponent("\(container.name).sqlite")

        var defaultURL: URL?
        if let storeDescription = container.persistentStoreDescriptions.first, let url = storeDescription.url {
            defaultURL = FileManager.default.fileExists(atPath: url.path) ? url : nil
        }

        if defaultURL == nil {
            container.persistentStoreDescriptions = [NSPersistentStoreDescription(url: storeURL)]
        }


        let description = container.persistentStoreDescriptions.first else {
            fatalError("Hey Listen! ###\(#function): Failed to retrieve a persistent store description.")
        }

        description.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
        if !useCloudSync {
            description.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
        }

        container.loadPersistentStores(completionHandler: { (storeDescription, error) in

            //migrate from old url to use app groups
            if let url = defaultURL, url.absoluteString != storeURL.absoluteString {
                let coordinator = container.persistentStoreCoordinator
                if let oldStore = coordinator.persistentStore(for: url) {
                    do {
                        try coordinator.migratePersistentStore(oldStore, to: storeURL, options: nil, withType: NSSQLiteStoreType)
                    } catch {
                        print("Hey Listen! Error migrating persistent store")
                        print(error.localizedDescription)
                    }

                    // delete old store
                    let fileCoordinator = NSFileCoordinator(filePresenter: nil)
                    fileCoordinator.coordinate(writingItemAt: url, options: .forDeleting, error: nil, byAccessor: { url in
                        do {
                            try FileManager.default.removeItem(at: url)
                        } catch {
                            print("Hey Listen! Error deleting old persistent store")
                            print(error.localizedDescription)
                        }
                    })
                }
            }
         }

         return container
   }
}

Answer 1

If you are still facing the same problem, you should add the following line for the storeDescription

storeDescription.cloudKitContainerOptions = NSPersistentCloudKitContainerOptions(containerIdentifier: "iCloud.com.yourapp.identifier")

Source: https://developer.apple.com/videos/play/wwdc2019/202/

Following is my CoreDataStack:

import CoreData

class CoreDataStack {
    // MARK: - Core Data stack

    static var persistentContainer: NSPersistentCloudKitContainer = {
        /*
         The persistent container for the application. This implementation
         creates and returns a container, having loaded the store for the
         application to it. This property is optional since there are legitimate
         error conditions that could cause the creation of the store to fail.
        */
        let container = NSPersistentCloudKitContainer(name: "data")
        
        let storeURL = URL.storeURL(for: "group.com.myapp", databaseName: "data")
        let storeDescription = NSPersistentStoreDescription(url: storeURL)
        storeDescription.cloudKitContainerOptions = NSPersistentCloudKitContainerOptions(containerIdentifier: "iCloud.com.myapp")
        container.persistentStoreDescriptions = [storeDescription]
        
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {
                // Replace this implementation with code to handle the error appropriately.
                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
                 
                /*
                 Typical reasons for an error here include:
                 * The parent directory does not exist, cannot be created, or disallows writing.
                 * The persistent store is not accessible, due to permissions or data protection when the device is locked.
                 * The device is out of space.
                 * The store could not be migrated to the current model version.
                 Check the error message to determine what the actual problem was.
                 */
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
        })
        return container
    }()
    


    // MARK: - Core Data Saving support

    static func saveContext () {
        let context = persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.save()
            } catch {
                // Replace this implementation with code to handle the error appropriately.
                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
                let nserror = error as NSError
                fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
            }
        }
    }
}

public extension URL {
    /// Returns a URL for the given app group and database pointing to the sqlite database.
    static func storeURL(for appGroup: String, databaseName: String) -> URL {
        guard let fileContainer = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: appGroup) else {
            fatalError("Shared file container could not be created.")
        }

        return fileContainer.appendingPathComponent("\(databaseName).sqlite")
    }
}