iOS - CoreData CloudKit sharing - participants adding children - ios

Question

I have implemented sharing of items from my Core Data store, using the NSPersistentCloudKitContainer api, with limited success. The objects I share (a TripsLog) have child objects (Trip), which appear on participants' devices. I've implemented more or less a direct copy of Apple's example code, except using my own core data entities.
The problem is that any new trips I create on participants' devices don't appear in the owner's database, whereas any I create on the owner's device appear for all participants, updating their displays pretty much instantly. If I edit any of the original trips on a participant's device, the changes are successfully shared, it's just the new ones which are problematic.
I'm getting a lot of noise in the console -
"Attempt to map database failed: permission was denied. This attempt will not be retried"
"Permission Failure" (10/2007); server message = "Invalid bundle ID for container"
etc
which really aren't helpful. The bundle ID & containers are set up properly and it all works fine for syncing across a single user's devices.
Although my code is more-or-less just the same as Apple's, except for the container identifier & the Core Data entities, here's most of the relevant stuff -
// sharing protocol
protocol CloudKitSharable: NSManagedObject {
static var entityName: String { get }
var identifier: String { get }
var sharedTitle: String { get }
var sharedSubject: String? { get }
var thumbnailImage: UIImage? { get }
}
class PersistenceController: NSObject {
enum CoreDataError: Error {
case modelURLNotFound(forResourceName: String)
case modelLoadingFailed(forURL: URL)
}
static let shared = PersistenceController()
private static let containerIdentifier = "iCloud.com.containerIdentifier"
private var _privatePersistentStore: NSPersistentStore?
var privatePersistentStore: NSPersistentStore {
return _privatePersistentStore!
}
private var _sharedPersistentStore: NSPersistentStore?
var sharedPersistentStore: NSPersistentStore {
return _sharedPersistentStore!
}
lazy var cloudKitContainer: CKContainer = {
return CKContainer(identifier: Self.containerIdentifier)
}()
lazy var persistentContainer: NSPersistentCloudKitContainer = {
let container: NSPersistentCloudKitContainer = try! mainDatabaseContainer()
guard let localDatabaseURL = localDatabaseURL, let cloudDatabaseURL = cloudDatabaseURL else {
fatalError("#\(#function): Failed to get local database URLs")
}
// Set up the database which will sync over the cloud
let cloudStoreDescription = NSPersistentStoreDescription(url: cloudDatabaseURL)
cloudStoreDescription.configuration = "Cloud"
cloudStoreDescription.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
setupStoreDescription(cloudStoreDescription)
let cloudKitContainerOptions = NSPersistentCloudKitContainerOptions(containerIdentifier: Self.containerIdentifier)
cloudKitContainerOptions.databaseScope = .private
cloudStoreDescription.cloudKitContainerOptions = cloudKitContainerOptions
// Setting up for sharing
let sharedStoreDescription = cloudStoreDescription.copy() as! NSPersistentStoreDescription
sharedStoreDescription.url = sharedDatabaseURL
let sharedStoreOptions = NSPersistentCloudKitContainerOptions(containerIdentifier: Self.containerIdentifier)
sharedStoreOptions.databaseScope = .shared
sharedStoreDescription.cloudKitContainerOptions = sharedStoreOptions
// Set up the stuff which we don't want to sync to the cloud
let localStoreDescription = NSPersistentStoreDescription(url: localDatabaseURL)
localStoreDescription.configuration = "Local"
setupStoreDescription(localStoreDescription)
// finish setting up the container
container.persistentStoreDescriptions = [
cloudStoreDescription,
localStoreDescription,
sharedStoreDescription
]
loadPersistentStores(for: container)
container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
container.viewContext.transactionAuthor = TransactionAuthor.app
/**
Automatically merge the changes from other contexts.
*/
container.viewContext.automaticallyMergesChangesFromParent = true
/**
Pin the viewContext to the current generation token and set it to keep itself up-to-date with local changes.
*/
do {
try container.viewContext.setQueryGenerationFrom(.current)
} catch {
fatalError("#\(#function): Failed to pin viewContext to the current generation:\(error)")
}
/**
Observe the following notifications:
- The remote change notifications from container.persistentStoreCoordinator.
- The .NSManagedObjectContextDidSave notifications from any context.
- The event change notifications from the container.
*/
NotificationCenter.default.addObserver(self, selector: #selector(storeRemoteChange(_:)),
name: .NSPersistentStoreRemoteChange,
object: container.persistentStoreCoordinator)
NotificationCenter.default.addObserver(self, selector: #selector(containerEventChanged(_:)),
name: NSPersistentCloudKitContainer.eventChangedNotification,
object: container)
return container
}()
func mergeTransactions(_ transactions: [NSPersistentHistoryTransaction], to context: NSManagedObjectContext) {
context.perform {
for transaction in transactions {
context.mergeChanges(fromContextDidSave: transaction.objectIDNotification())
}
}
}
private var cloudDatabaseURL: URL? {
return UIApplication.applicationSupportDirectory?.appendingPathComponent("CloudDatabase.sqlite")
}
private var localDatabaseURL: URL? {
return UIApplication.applicationSupportDirectory?.appendingPathComponent("Database.sqlite")
}
private var sharedDatabaseURL: URL? {
return UIApplication.applicationSupportDirectory?.appendingPathComponent("Shared.sqlite")
}
private func setupStoreDescription(_ description: NSPersistentStoreDescription) {
description.setOption(true as NSNumber, forKey: NSMigratePersistentStoresAutomaticallyOption)
description.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
description.shouldInferMappingModelAutomatically = true
}
private func model(name: String) throws -> NSManagedObjectModel {
return try loadModel(name: name, bundle: Bundle.main)
}
private func loadModel(name: String, bundle: Bundle) throws -> NSManagedObjectModel {
guard let modelURL = bundle.url(forResource: name, withExtension: "momd") else {
throw CoreDataError.modelURLNotFound(forResourceName: name)
}
guard let model = NSManagedObjectModel(contentsOf: modelURL) else {
throw CoreDataError.modelLoadingFailed(forURL: modelURL)
}
return model
}
private func mainDatabaseContainer() throws -> NSPersistentCloudKitContainer {
return NSPersistentCloudKitContainer(name: "Database", managedObjectModel: try model(name: "Database"))
}
private func locationsContainer() throws -> NSPersistentContainer {
return NSPersistentContainer(name: "Locations", managedObjectModel: try model(name: "Locations"))
}
private func loadPersistentStores(for container: NSPersistentContainer) {
container.loadPersistentStores { [unowned self] storeDescription, error in
if let error = error {
fatalError("#\(#function): Failed to load persistent stores:\(error)")
} else {
print("Database store ok: ", storeDescription)
if let containerOptions = storeDescription.cloudKitContainerOptions, let url = self.sharedDatabaseURL {
if containerOptions.databaseScope == .shared {
let sharedStore = container.persistentStoreCoordinator.persistentStore(for: url)
self._sharedPersistentStore = sharedStore
}
} else if let url = self.cloudDatabaseURL {
let privateStore = container.persistentStoreCoordinator.persistentStore(for: url)
self._privatePersistentStore = privateStore
}
}
}
}
/**
An operation queue for handling history-processing tasks: watching changes, deduplicating tags, and triggering UI updates, if needed.
*/
lazy var historyQueue: OperationQueue = {
let queue = OperationQueue()
queue.maxConcurrentOperationCount = 1
return queue
}()
}
// Sharing extensions
extension PersistenceController {
func presentCloudSharingController<T: CloudKitSharable>(for item: T) {
/**
Grab the share if the item is already shared.
*/
var itemToShare: CKShare?
if let shareSet = try? persistentContainer.fetchShares(matching: [item.objectID]), let (_, share) = shareSet.first {
itemToShare = share
}
let sharingController: UICloudSharingController
if let itemToShare = itemToShare {
sharingController = UICloudSharingController(share: itemToShare, container: cloudKitContainer)
} else {
sharingController = newSharingController(for: item)
}
sharingController.delegate = self
/**
Setting the presentation style to .formSheet so there's no need to specify sourceView, sourceItem, or sourceRect.
*/
if let viewController = rootViewController {
sharingController.modalPresentationStyle = .formSheet
viewController.present(sharingController, animated: true)
}
}
func presentCloudSharingController(share: CKShare) {
let sharingController = UICloudSharingController(share: share, container: cloudKitContainer)
sharingController.delegate = self
/**
Setting the presentation style to .formSheet so there's no need to specify sourceView, sourceItem, or sourceRect.
*/
if let viewController = rootViewController {
sharingController.modalPresentationStyle = .formSheet
viewController.present(sharingController, animated: true)
}
}
private func newSharingController<T: CloudKitSharable>(for unsharedItem: T) -> UICloudSharingController {
return UICloudSharingController { (_, completion: #escaping (CKShare?, CKContainer?, Error?) -> Void) in
/**
The app doesn't specify a share intentionally, so Core Data creates a new share (zone).
CloudKit has a limit on how many zones a database can have, so this app provides an option for users to use an existing share.
If the share's publicPermission is CKShareParticipantPermissionNone, only private participants can accept the share.
Private participants mean the participants an app adds to a share by calling CKShare.addParticipant.
If the share is more permissive, and is, therefore, a public share, anyone with the shareURL can accept it,
or self-add themselves to it.
The default value of publicPermission is CKShare.ParticipantPermission.none.
*/
self.persistentContainer.share([unsharedItem], to: nil) { objectIDs, share, container, error in
if let share = share {
self.configure(share: share, with: unsharedItem)
}
completion(share, container, error)
}
}
}
private var rootViewController: UIViewController? {
for scene in UIApplication.shared.connectedScenes {
if scene.activationState == .foregroundActive,
let sceneDelegate = (scene as? UIWindowScene)?.delegate as? UIWindowSceneDelegate,
let window = sceneDelegate.window {
return window?.rootViewController
}
}
print("\(#function): Failed to retrieve the window's root view controller.")
return nil
}
}
extension PersistenceController: UICloudSharingControllerDelegate {
/**
CloudKit triggers the delegate method in two cases:
- An owner stops sharing a share.
- A participant removes themselves from a share by tapping the Remove Me button in UICloudSharingController.
After stopping the sharing, purge the zone or just wait for an import to update the local store.
This sample chooses to purge the zone to avoid stale UI. That triggers a "zone not found" error because UICloudSharingController
deletes the zone, but the error doesn't really matter in this context.
Purging the zone has a caveat:
- When sharing an object from the owner side, Core Data moves the object to the shared zone.
- When calling purgeObjectsAndRecordsInZone, Core Data removes all the objects and records in the zone.
To keep the objects, deep copy the object graph you want to keep and make sure no object in the new graph is associated with any share.
The purge API posts an NSPersistentStoreRemoteChange notification after finishing its job, so observe the notification to update
the UI, if necessary.
*/
func cloudSharingControllerDidStopSharing(_ csc: UICloudSharingController) {
if let share = csc.share {
purgeObjectsAndRecords(with: share)
}
}
func cloudSharingControllerDidSaveShare(_ csc: UICloudSharingController) {
if let share = csc.share, let persistentStore = share.persistentStore {
persistentContainer.persistUpdatedShare(share, in: persistentStore) { (share, error) in
if let error = error {
print("\(#function): Failed to persist updated share: \(error)")
}
}
}
}
func cloudSharingController(_ csc: UICloudSharingController, failedToSaveShareWithError error: Error) {
print("\(#function): Failed to save a share: \(error)")
}
func itemTitle(for csc: UICloudSharingController) -> String? {
return csc.share?.title ?? "Airframe Logbook"
}
}
extension PersistenceController {
func shareObject<T: CloudKitSharable>(_ unsharedObject: T, to existingShare: CKShare?, completionHandler: ((_ share: CKShare?, _ error: Error?) -> Void)? = nil) {
persistentContainer.share([unsharedObject], to: existingShare) { (objectIDs, share, container, error) in
guard error == nil, let share = share else {
print("\(#function): Failed to share an object: \(error!))")
completionHandler?(share, error)
return
}
/**
Deduplicate tags, if necessary, because adding a photo to an existing share moves the whole object graph to the associated
record zone, which can lead to duplicated tags.
*/
if existingShare != nil {
/*
if let tagObjectIDs = objectIDs?.filter({ $0.entity.name == "Tag" }), !tagObjectIDs.isEmpty {
self.deduplicateAndWait(tagObjectIDs: Array(tagObjectIDs))
}
*/
} else {
self.configure(share: share, with: unsharedObject)
}
/**
Synchronize the changes on the share to the private persistent store.
*/
self.persistentContainer.persistUpdatedShare(share, in: self.privatePersistentStore) { (share, error) in
if let error = error {
print("\(#function): Failed to persist updated share: \(error)")
}
completionHandler?(share, error)
}
}
}
/**
Delete the Core Data objects and the records in the CloudKit record zone associated with the share.
*/
func purgeObjectsAndRecords(with share: CKShare, in persistentStore: NSPersistentStore? = nil) {
guard let store = (persistentStore ?? share.persistentStore) else {
print("\(#function): Failed to find the persistent store for share. \(share))")
return
}
persistentContainer.purgeObjectsAndRecordsInZone(with: share.recordID.zoneID, in: store) { (zoneID, error) in
if let error = error {
print("\(#function): Failed to purge objects and records: \(error)")
}
}
}
func existingShare(for item: NSManagedObject) -> CKShare? {
if let shareSet = try? persistentContainer.fetchShares(matching: [item.objectID]),
let (_, share) = shareSet.first {
return share
}
return nil
}
func share(with title: String) -> CKShare? {
let stores = [privatePersistentStore, sharedPersistentStore]
let shares = try? persistentContainer.fetchShares(in: stores)
let share = shares?.first(where: { $0.title == title })
return share
}
func shareTitles() -> [String] {
let stores = [privatePersistentStore, sharedPersistentStore]
let shares = try? persistentContainer.fetchShares(in: stores)
return shares?.map { $0.title } ?? []
}
private func configure<T: CloudKitSharable>(share: CKShare, with item: T) {
share[CKShare.SystemFieldKey.title] = item.sharedTitle
}
}
extension PersistenceController {
func addParticipant(emailAddress: String, permission: CKShare.ParticipantPermission = .readWrite, share: CKShare,
completionHandler: ((_ share: CKShare?, _ error: Error?) -> Void)?) {
/**
Use the email address to look up the participant from the private store. Return if the participant doesn't exist.
Use privatePersistentStore directly because only the owner may add participants to a share.
*/
let lookupInfo = CKUserIdentity.LookupInfo(emailAddress: emailAddress)
let persistentStore = privatePersistentStore //share.persistentStore!
persistentContainer.fetchParticipants(matching: [lookupInfo], into: persistentStore) { (results, error) in
guard let participants = results, let participant = participants.first, error == nil else {
completionHandler?(share, error)
return
}
participant.permission = permission
participant.role = .privateUser
share.addParticipant(participant)
self.persistentContainer.persistUpdatedShare(share, in: persistentStore) { (share, error) in
if let error = error {
print("\(#function): Failed to persist updated share: \(error)")
}
completionHandler?(share, error)
}
}
}
func deleteParticipant(_ participants: [CKShare.Participant], share: CKShare,
completionHandler: ((_ share: CKShare?, _ error: Error?) -> Void)?) {
for participant in participants {
share.removeParticipant(participant)
}
/**
Use privatePersistentStore directly because only the owner may delete participants to a share.
*/
persistentContainer.persistUpdatedShare(share, in: privatePersistentStore) { (share, error) in
if let error = error {
print("\(#function): Failed to persist updated share: \(error)")
}
completionHandler?(share, error)
}
}
}
// Core Data models
extension TripsLog {
#NSManaged var name: String
#NSManaged var identifier: String
#NSManaged var entries: NSSet
}
extension Trip {
#NSManaged var identifier: String
#NSManaged var name: String
#NSManaged var date: Date
#NSManaged var comments: String?
#NSManaged var leaderName: String
#NSManaged var images: NSSet?
}
If anyone is able to shed any light on this I'd really appreciate it, as Apple's own documentation is somewhat lacking. Many thanks!