Every time I insert a subclass (MYShapeLayer) into the model context, the app crashes with an error:
DesignerPlayground crashed due to fatalError in BackingData.swift at line 908. Never access a full future backing data - PersistentIdentifier(id: SwiftData.PersistentIdentifier.ID(backing: SwiftData.PersistentIdentifier.PersistentIdentifierBacking.managedObjectID(0xb2dbc55f3f4c57f2 <x-coredata://B1E3206B-40DE-4185-BC65-4540B4705B40/MYShapeLayer/p1>))) with Optional(A6CA4F89-107F-4A66-BC49-DD7DAC689F77)
struct ContentView: View {
@Environment(\.modelContext) private var modelContext
@Query private var designs: [MYDesign]
var layers: [MYLayer] {
designs.first?.layers ?? []
}
var body: some View {
NavigationStack {
List {
ForEach(layers) { layer in
Text(layer.description)
}
}
.onAppear {
let design = MYDesign(title: "My Design")
modelContext.insert(design)
try? modelContext.save()
}
.toolbar {
Menu("Add", systemImage: "plus") {
Button(action: addTextLayer) {
Text("Add Text Layer")
}
Button(action: addShapeLayer) {
Text("Add Shape Layer")
}
}
}
}
}
private func addTextLayer() {
if let design = designs.first {
let newLayer = MYLayer(order: layers.count, kind: .text)
newLayer.design = design
modelContext.insert(newLayer)
try? modelContext.save()
}
}
private func addShapeLayer() {
if let design = designs.first {
let newLayer = MYShapeLayer(shapeName: "Ellipse", order: layers.count)
newLayer.design = design
modelContext.insert(newLayer)
try? modelContext.save()
}
}
}
#Preview {
ContentView()
.modelContainer(for: [MYDesign.self, MYLayer.self, MYShapeLayer.self], inMemory: true)
}
@Model
final class MYDesign {
var title: String = ""
@Relationship(deleteRule: .cascade, inverse: \MYLayer.design)
var layers: [MYLayer] = []
init(title: String = "") {
self.title = title
}
}
@available(iOS 26.0, macOS 26.0, *)
@Model
class MYLayer {
var design: MYDesign!
var order: Int = 0
var title: String = ""
init(order: Int = 0, title: String = "New Layer") {
self.order = order
self.title = title
}
}
@available(iOS 26.0, macOS 26.0, *)
@Model
class MYShapeLayer: MYLayer {
var shapeName: String = ""
init(shapeName: String, order: Int = 0) {
self.shapeName = shapeName
super.init(order: order)
}
}
iCloud & Data
RSS for tagLearn how to integrate your app with iCloud and data frameworks for effective data storage
Selecting any option will automatically load the page
Post
Replies
Boosts
Views
Activity
Starting 20th March 2025, I see an increase in bandwidth and latency for one of my CloudKit projects.
I'm using NSPersistentCloudKitContainer to synchronise my data.
I haven't changed any CloudKit scheme during that time but shipped an update. Since then, I reverted some changes from that update, which could have led to changes in the sync behaviour.
Is anyone else seeing any issues?
I would love to file a DTS and use one of my credits for that, but unfortunately, I can't because I cannot reproduce it with a demo project because I cannot travel back in time and check if it also has an increase in metrics during that time.
Maybe an Apple engineer can green-light me filing a DTS request, please.
I'm getting the following error message when executing the rollback method in a modelContext, what could be causing this ?
SwiftData/ModelSnapshot.swift:46: Fatal error: A ModelSnapshot must be initialized with a known-keys dictionary
Hi,
I did cloudkit synchronization using swiftdata.
However, synchronization does not occur automatically, and synchronization occurs intermittently only when the device is closed and opened.
For confirmation, after changing the data in Device 1 (saving), when the data is fetched from Device 2, there is no change.
I've heard that there's still an issue with swiftdata sync and Apple is currently troubleshooting it, is the phenomenon I'm experiencing in the current version normal?
Hello Apple Team,
We are looking at developing an iOS feature on our current development that stores user-generated images as CKAssets in the public CloudKit database, with access control enforced by our app’s own logic (not CloudKit Sharing as that has a limit of 100 shares per device). Each story or post is a public record, and users only see content based on buddy relationships handled within the app.
We’d like to confirm that this pattern is consistent with Apple’s best practices for social features. Specifically:
Is it acceptable to store user-uploaded CKAssets in the public CloudKit database, as long as access visibility is enforced by the app?
Are there any performance or quota limitations (e.g., storage, bandwidth, or user sync limits) that apply to CKAssets in the public database when used at scale?
Would CloudKit Sharing be recommended instead, even if we don’t require user-to-user sharing invitations?
For App Review, is this model (public CKAssets + app-enforced access control) compliant with Apple’s data and security expectations?
Are there any caching or bandwidth optimization guidelines for handling image-heavy public CKAsset data in CloudKit?
Thanks again for your time
If I have two consecutive calls like to perform(schedule: .immediate) like so:
func doSomething() async {
await self.perform(schedule: .immediate) {
// add log event 1 to data store
}
await self.perform(schedule: .immediate) {
// add log event 2 to data store
}
}
Can I be guaranteed that the block for log event 1 will happen after log event 2?
"log event" here is just an example, so please ignore things like storing date, etc.
Looking at the documentation here:
https://developer.apple.com/documentation/coredata/nsmanagedobjectcontext/perform(schedule:_:)
It's a little unclear whether any such guarantee is in place. However, given that the function returns the value from the block, it seems like I should be able to expect event 1 will always be executed before event 2 regardless of the schedule parameter?
Hello,
SwiftData is not working correctly with Swift Concurrency. And it’s sad after all this time.
I personally found a regression. The attached code works perfectly fine on iOS 17.5 but doesn’t work correctly on iOS 18 or iOS 18.1.
A model can be updated from the background (Task, Task.detached or ModelActor) and refreshes the UI, but as soon as the same item is updated from the View (fetched via a Query), the next background updates are not reflected anymore in the UI, the UI is not refreshed, the updates are not merged into the main.
How to reproduce:
Launch the app
Tap the plus button in the navigation bar to create a new item
Tap on the “Update from Task”, “Update from Detached Task”, “Update from ModelActor” many times
Notice the time is updated
Tap on the “Update from View” (once or many times)
Notice the time is updated
Tap again on “Update from Task”, “Update from Detached Task”, “Update from ModelActor” many times
Notice that the time is not update anymore
Am I doing something wrong? Or is this a bug in iOS 18/18.1?
Many other posts talk about issues where updates from background thread are not merged into the main thread. I don’t know if they all are related but it would be nice to have
1/ bug fixed, meaning that if I update an item from a background, it’s reflected in the UI, and
2/ proper documentation on how to use SwiftData with Swift Concurrency (ModelActor). I don’t know if what I’m doing in my buttons is correct or not.
Thanks,
Axel
import SwiftData
import SwiftUI
@main
struct FB_SwiftData_BackgroundApp: App {
var body: some Scene {
WindowGroup {
ContentView()
.modelContainer(for: Item.self)
}
}
}
struct ContentView: View {
@Environment(\.modelContext) private var modelContext
@State private var simpleModelActor: SimpleModelActor!
@Query private var items: [Item]
var body: some View {
NavigationView {
VStack {
if let firstItem: Item = items.first {
Text(firstItem.timestamp, format: Date.FormatStyle(date: .omitted, time: .standard))
.font(.largeTitle)
.fontWeight(.heavy)
Button("Update from Task") {
let modelContainer: ModelContainer = modelContext.container
let itemID: Item.ID = firstItem.persistentModelID
Task {
let context: ModelContext = ModelContext(modelContainer)
guard let itemInContext: Item = context.model(for: itemID) as? Item else { return }
itemInContext.timestamp = Date.now.addingTimeInterval(.random(in: 0...2000))
try context.save()
}
}
.buttonStyle(.bordered)
Button("Update from Detached Task") {
let container: ModelContainer = modelContext.container
let itemID: Item.ID = firstItem.persistentModelID
Task.detached {
let context: ModelContext = ModelContext(container)
guard let itemInContext: Item = context.model(for: itemID) as? Item else { return }
itemInContext.timestamp = Date.now.addingTimeInterval(.random(in: 0...2000))
try context.save()
}
}
.buttonStyle(.bordered)
Button("Update from ModelActor") {
let container: ModelContainer = modelContext.container
let persistentModelID: Item.ID = firstItem.persistentModelID
Task.detached {
let actor: SimpleModelActor = SimpleModelActor(modelContainer: container)
await actor.updateItem(identifier: persistentModelID)
}
}
.buttonStyle(.bordered)
Button("Update from ModelActor in State") {
let container: ModelContainer = modelContext.container
let persistentModelID: Item.ID = firstItem.persistentModelID
Task.detached {
let actor: SimpleModelActor = SimpleModelActor(modelContainer: container)
await MainActor.run {
simpleModelActor = actor
}
await actor.updateItem(identifier: persistentModelID)
}
}
.buttonStyle(.bordered)
Divider()
.padding(.vertical)
Button("Update from View") {
firstItem.timestamp = Date.now.addingTimeInterval(.random(in: 0...2000))
}
.buttonStyle(.bordered)
} else {
ContentUnavailableView(
"No Data",
systemImage: "slash.circle", //
description: Text("Tap the plus button in the toolbar")
)
}
}
.toolbar {
ToolbarItem(placement: .primaryAction) {
Button(action: addItem) {
Label("Add Item", systemImage: "plus")
}
}
}
}
}
private func addItem() {
modelContext.insert(Item(timestamp: Date.now))
try? modelContext.save()
}
}
@ModelActor
final actor SimpleModelActor {
var context: String = ""
func updateItem(identifier: Item.ID) {
guard let item = self[identifier, as: Item.self] else {
return
}
item.timestamp = Date.now.addingTimeInterval(.random(in: 0...2000))
try! modelContext.save()
}
}
@Model
final class Item: Identifiable {
var timestamp: Date
init(timestamp: Date) {
self.timestamp = timestamp
}
}
Hi all,
I’m encountering a consistent issue with SwiftData on watchOS when using CloudKit sync. After enabling:
let config = ModelConfiguration(schema: schema, cloudKitDatabase: .automatic)
…the app terminates ~30–60 seconds into a WKExtendedRuntimeSession. This happens specifically when:
Always-On Display is OFF
The iPhone is disconnected or in Airplane Mode
The app is running in a WKExtendedRuntimeSession (e.g., used for meditation tracking)
The Xcode logs show a warning:
Background Task ("CoreData: CloudKit Setup"), was created over 30 seconds ago. In applications running in the background, this creates a risk of termination.
It appears CloudKit sync setup is being triggered automatically and flagged by the system as an unmanaged long-running task, leading to termination.
Workaround:
Switching to:
let config = ModelConfiguration(schema: schema, cloudKitDatabase: .none)
…prevents the issue entirely — no background task warning, no crash.
Feedback ID submitted: FB17685611
Just wanted to check if others have seen this behavior or found alternative solutions. It seems like something Apple may need to address in SwiftData’s CloudKit handling on watchOS.
Topic:
App & System Services
SubTopic:
iCloud & Data
Tags:
CloudKit
watchOS
Background Tasks
SwiftData
My iOS app uses CloudKit key-value storage. I have not updated the app in a few years but it works fine. Since it was last updated, I transferred the app from an old organization to my personal developer account. Now that I'm working on the app again I get an error: Provisioning profile "iOS Team Provisioning Profile: com.company.app" doesn't match the entitlements file's value for the com.apple.developer.ubiquity-kvstore-identifier entitlement.
In the entitlement file, it has $(TeamIdentifierPrefix)$(CFBundleIdentifier) as the value for iCloud Key-Value Store. I've verified the variables resolve as expected. When I parse the provisioning profile there is no entitlement value for key-value storage. What am I getting wrong?
I have an app that from day 1 has used Swiftdata and successfully sync'd across devices with Cloudkit. I have added models to the data in the past and deployed the schema and it continued to sync across devices. Sometime I think in June.2025 I added a new model and built out the UI to display and manage it. I pushed a version to Test Flight (twice over a matter of 2 versions and a couple of weeks) and created objects in the new model in Test Flight versions of the app which should push the info to Cloudkit to update the schema.
When I go to deploy the schema though there are no changes. I confirmed in the app that Cloudkit is selected and it's point to the correct container. And when I look in Cloudkit the new model isn't listed as an indes.
I've pushed deploy schema changes anyway (more than once) and now the app isn't sync-ing across devices at all (even the pre-existing models aren't sync-ing across devices).
I even submitted the first updated version to the app store and it was approved and released. I created objects in the new model in production which I know doesn't create the indexes in the development environment. But this new model functions literally everywhere except Cloudkit and I don't know what else to do to trigger an update.
Perhaps I just have the wrong expectations, but I discovered some odd behavior from SwiftData that sure seems like a bug to me...
If you make any change to any SwiftData model object — even just setting a property to its current value — every SwiftUI view that uses SwiftData is rebuilt. Every query and every entity reference, even if the property was set on a model class that is completely unrelated to the view.
SwiftUI does such a good job of optimizing UI updates that it's hard to notice the issue. I only noticed it because the updates were triggering my debug print statements.
To double-check this, I went back to Apple's new iOS app template — the one that is just a list of dated items — and added a little code to touch an unrelated record in the background:
@Model
class UnrelatedItem {
var name: String
init(name: String) {
self.name = name
}
}
@main
struct jumpyApp: App {
var sharedModelContainer: ModelContainer = {
let schema = Schema([
Item.self,
UnrelatedItem.self
])
let modelConfiguration = ModelConfiguration(schema: schema, isStoredInMemoryOnly: false)
do {
return try ModelContainer(for: schema, configurations: [modelConfiguration])
} catch {
fatalError("Could not create ModelContainer: \(error)")
}
}()
init() {
let context = sharedModelContainer.mainContext
// Create 3 items at launch so we immediately have some data to work with.
if try! context.fetchCount(FetchDescriptor<Item>()) == 0 {
for _ in 0..<3 {
let item = Item(timestamp: Date())
context.insert(item)
}
}
// Now create one unrelated item.
let unrelatedItem = UnrelatedItem(name: "Mongoose")
context.insert(unrelatedItem)
try? context.save()
// Set up a background task that updates the unrelated item every second.
Task {
while true {
try? await Task.sleep(nanoseconds: 1_000_000_000)
Task { @MainActor in
// We don't even have to change the name or save the contxt.
// Just setting the name to the same value will trigger a change.
unrelatedItem.name = "Mongoose"
}
}
}
}
var body: some Scene {
WindowGroup {
ContentView()
}
.modelContainer(sharedModelContainer)
}
}
I also added a print statement to the ContentView so I could see when the view updates.
struct ContentView: View {
@Environment(\.modelContext) private var modelContext
@Query private var items: [Item]
var body: some View {
NavigationSplitView {
List {
let _ = Self._printChanges()
...
The result is that the print statement logs 2 messages to the debug console every second. I checked in iOS 17, 18.1, and 18.2, and they all behave this way.
Is this the intended behavior? I thought the whole point of the new Observation framework in iOS 17 was to track which data had changed and only send change notifications to observers who were using that data.
I am a novice developer, so please be kind. 😬
I am developing a simple macOS app backed with SwiftData and trying to set up iCloud sync so data syncs between two Macs running the app. I have added the iCloud capability, checked the CloudKit box, and selected an iCloud Container. Per suggestion of Paul Hudson, my model properties have either default values or are marked as optional, and the only relationship in my model is marked as optional.
@Model
final class Project {
// Stable identifier used for restoring selected project across launches.
var uuid: UUID?
var name: String = ""
var active: Bool = true
var created: Date = Foundation.Date(timeIntervalSince1970: 0)
var modified: Date = Foundation.Date(timeIntervalSince1970: 0)
// CloudKit requires to-many relationships to be optional in this schema.
@Relationship
var timeEntries: [TimeEntry]?
init(name: String, active: Bool = true, uuid: UUID? = UUID()) {
self.uuid = uuid
self.name = name
self.active = active
self.created = .now
self.modified = .now
self.timeEntries = []
}
@Model
final class TimeEntry {
// Core timing fields.
var start: Date = Foundation.Date(timeIntervalSince1970: 0)
var end: Date = Foundation.Date(timeIntervalSince1970: 0)
var codeRawValue: String?
var activitiesRawValue: String = ""
// Inverse relationship back to the owning project.
@Relationship(inverse: \Project.timeEntries)
var project: Project?
init(
start: Date = .now,
end: Date = .now.addingTimeInterval(60 * 60),
code: BillingCode? = nil,
activities: [ActivityType] = []
) {
self.start = start
self.end = end
self.codeRawValue = code?.rawValue
self.activitiesRawValue = Self.serializeActivities(activities)
}
I have set up the following in the AppDelegate for registering for remote notifications as well as some logging to console that the remote notification token was received and to be notified when when I am receiving remote notifications.
private final class TimeTrackerAppDelegate: NSObject, NSApplicationDelegate {
func applicationDidFinishLaunching(_ notification: Notification) {
print("📡 [Push] Registering for remote notifications")
NSApplication.shared.registerForRemoteNotifications()
}
func application(_ application: NSApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
let tokenPreview = deviceToken.map { String(format: "%02x", $0) }.joined().prefix(16)
print("✅ [Push] Registered for remote notifications (token prefix: \(tokenPreview)...)")
}
func application(_ application: NSApplication, didFailToRegisterForRemoteNotificationsWithError error: Error) {
let nsError = error as NSError
print("❌ [Push] Failed to register for remote notifications: \(nsError.domain) (\(nsError.code)) \(nsError.localizedDescription)")
}
func application(_ application: NSApplication, didReceiveRemoteNotification userInfo: [String: Any]) {
print("📬 [Push] Received remote notification: \(userInfo)")
}
}
In testing, I run the same commit from Xcode on two different Macs logged into the same iCloud account.
My problem is that sync is not reliably working. Starting up the app on both Macs shows that the app successfully registered for remote notifications.
Sometimes, making an edit on Mac 1 is immediately reflected in Mac 2 UI along with didReceiveRemoteNotification message (all occurring while the Mac 2 app remains in foreground). Sometimes, the Mac 2 app needs to be backgrounded and re-foregrounded before the UI shows the updated data.
Sometimes, an edit on Mac 2 will show on Mac 1 only after re-foregrounded but not show any didReceiveRemoteNotification on the Mac 1 console.
Sometimes, an edit on Mac 2 will not show at all on Mac 1 even after re-foregrounding the app.
Sometimes, no edits sync between either Mac.
I had read about how a few years back, there was a bug in macOS where testing iCloud sync between Macs did not work while running from Xcode but would work in TestFlight. For me, running my app in TestFlight on both Macs has never been able to sync any edits between the Macs.
Any idea where I might be going wrong. It seems this should not be this hard and should not be failing so inconsistently. Wondering what I might be doing wrong here.
I’m building an app that edits files in iCloud and uses an NSFilePresenter to monitor changes.
When a conflict occurs, the system calls presentedItemDidGain(_:).
In that method, I merge the versions by reading the current (canonical) version using NSFileVersion.currentVersionOfItem(at:) and the conflicting ones using NSFileVersion.unresolvedConflictVersionsOfItem(at:).
This generally works, but sometimes, if two devices edit the same file at the same time, each device sees its own local version as the current one. For example:
Device A writes fileVerA (slightly later in real time)
Device B writes fileVerB
On Device A all works fine, currentVersionOfItem returns fileVerA, as expected, and unresolvedConflictVersionsOfItem returns [fileVerB].
But on Device B, currentVersionOfItem returns fileVerB!? And unresolvedConflictVersionsOfItem returns the same, local file [fileVerB], without any hint of the other conflicting version, fileVerA.
Later, the newer version from the Device A arrives on Device B as a normal, non-conflicting update via presentedItemDidChange(_:).
This seems to contradict Apple’s documentation:
“The currentVersionOfItemAtURL: method returns an NSFileVersion object representing what’s referred to as the current file; the current file is chosen by iCloud on some basis as the current “conflict winner” and is the same across all devices.”
Is this expected behavior, or a bug in how iCloud reports file versions?
I have some code which handles doing some computation on a background thread before updating Core Data NSManagedObjects by using the NSManagedObjectContext.perform functions.
This code is covered in Sendable warnings in Xcode 26 (beta 6) because my NSManagedObject subclasses (autogenerated) are non-Sendable and NSManagedObjectContext.perform function takes a Sendable closure.
But I can't really figure out what I should be doing. I realize this pattern is non-ideal for Swift concurrency, but it's what Core Data demands AFAIK. How do I deal with this?
let moc = object.managedObjectContext!
try await moc.perform {
object.completed = true // Capture of 'object' with non-Sendable type 'MySpecialObject' in a '@Sendable' closure
try moc.save()
}
Thanks in advance for your help!
I have a model with a FamilyActivitySelection, currently i'm using a codable struct to store it with UserDefaults, but would prefer strongly to transition to Swift Data
Hey everyone I just ran into an issue where I couldn't sync the model below fully by using CloudKit,
enum LinkMapV3_1: VersionedSchema {
static let versionIdentifier: Schema.Version = .init(3, 1, 0)
static var models: [any PersistentModel.Type] {
[AnnotationData.self, GroupData.self, Item.self, Deployment.self, History.self]
}
// MARK: - Data
@Model
class AnnotationData {
var name: String = ""
var longitude: Double = 0.0
var latitude: Double = 0.0
var order: Int = -1
var level: Int = 1
var detail: String = ""
@Relationship(deleteRule: .nullify, inverse: \GroupData.annotation)
var groups: [GroupData]?
@Relationship(deleteRule: .nullify, inverse: \AnnotationData.to)
var from: AnnotationData?
var to: AnnotationData?
var history: History?
}
// MARK: - History
@Model
class History {
var id: UUID = UUID()
var timestamp: Date = Date()
@Relationship(deleteRule: .nullify, inverse: \AnnotationData.history)
var annotations: [AnnotationData]?
@Relationship(deleteRule: .nullify, inverse: \GroupData.history)
var groups: [GroupData]?
@Relationship(deleteRule: .nullify, inverse: \Item.history)
var items: [Item]?
@Relationship(deleteRule: .nullify, inverse: \Deployment.history)
var deployment: Deployment?
var formattedDate: String {
let formatter = DateFormatter()
formatter.dateStyle = .medium
formatter.timeStyle = .short
return formatter.string(from: timestamp)
}
var timeAgo: String {
let formatter = RelativeDateTimeFormatter()
formatter.unitsStyle = .abbreviated
return formatter.localizedString(for: timestamp, relativeTo: Date())
}
}
}
So when trying to sync with the code in documentation
let modelContainer: ModelContainer
init() {
let config = ModelConfiguration()
typealias vs = LinkMapV3_1
do {
#if DEBUG
// Use an autorelease pool to make sure Swift deallocates the persistent
// container before setting up the SwiftData stack.
try autoreleasepool {
let desc = NSPersistentStoreDescription(url: config.url)
let opts = NSPersistentCloudKitContainerOptions(containerIdentifier: "iCloud.name.Endsunset.LinkMap.SwiftData.v1")
desc.cloudKitContainerOptions = opts
// Load the store synchronously so it completes before initializing the
// CloudKit schema.
desc.shouldAddStoreAsynchronously = false
if let mom = NSManagedObjectModel.makeManagedObjectModel(for: [vs.AnnotationData.self, vs.GroupData.self, vs.Item.self, vs.Deployment.self, vs.History.self]) {
let container = NSPersistentCloudKitContainer(name: "LinkMap", managedObjectModel: mom)
container.persistentStoreDescriptions = [desc]
container.loadPersistentStores {_, err in
if let err {
fatalError(err.localizedDescription)
}
}
// Initialize the CloudKit schema after the store finishes loading.
try container.initializeCloudKitSchema()
// Remove and unload the store from the persistent container.
if let store = container.persistentStoreCoordinator.persistentStores.first {
try container.persistentStoreCoordinator.remove(store)
}
}
}
#endif
modelContainer = try ModelContainer(for:
vs.AnnotationData.self,
vs.GroupData.self,
vs.Item.self,
vs.Deployment.self,
vs.History.self,
configurations: config)
} catch {
fatalError(error.localizedDescription)
}
}
The output is
Console Output
Where you can see
Output Extract
Optional arrays with @Relationship are missing, and the entry of record types on cloudkit database container are also missing it.
When I attempt to insert an annotation, I got
SwiftData/PersistentModel.swift:559: Fatal error: This KeyPath does not appear to relate AnnotationData to anything - \AnnotationData.groups
It gets more suspicious when restart the app and try again, the above error end with "AnnotationData.history", and if I tried again the above error end with "AnnotationData.from"... and so on.
No matter how my app stop working.
In my app, I've been using ModelActors in SwiftData, and using actors with a custom executor in Core Data to create concurrency safe services.
I have multiple actor services that relate to different data model components or features, each that have their own internally managed state (DocumentService, ImportService, etc).
The problem I've ran into, is that I need to be able to use multiple of these services within another service, and those services need to share the same context. Swift 6 doesn't allow passing contexts across actors.
The specific problem I have is that I need a master service that makes multiple unrelated changes without saving them to the main context until approved by the user.
I've tried to find a solution in SwiftData and Core Data, but both have the same problem which is contexts are not sendable. Read the comments in the code to see the issue:
/// This actor does multiple things without saving, until committed in SwiftData.
@ModelActor
actor DatabaseHelper {
func commitChange() throws {
try modelContext.save()
}
func makeChanges() async throws {
// Do unrelated expensive tasks on the child context...
// Next, use our item service
let service = ItemService(modelContainer: SwiftDataStack.shared.container)
let id = try await service.expensiveBackgroundTask(saveChanges: false)
// Now that we've used the service, we need to access something the service created.
// However, because the service created its own context and it was never saved, we can't access it.
let itemFromService = context.fetch(id) // fails
// We need to be able to access changes made from the service within this service,
/// so instead I tried to create the service by passing the current service context, however that results in:
// ERROR: Sending 'self.modelContext' risks causing data races
let serviceFromContext = ItemService(context: modelContext)
// Swift Data doesn't let you create child contexts, so the same context must be used in order to change data without saving.
}
}
@ModelActor
actor ItemService {
init(context: ModelContext) {
modelContainer = SwiftDataStack.shared.container
modelExecutor = DefaultSerialModelExecutor(modelContext: context)
}
func expensiveBackgroundTask(saveChanges: Bool = true) async throws -> PersistentIdentifier? {
// Do something expensive...
return nil
}
}
Core Data has the same problem:
/// This actor does multiple things without saving, until committed in Core Data.
actor CoreDataHelper {
let parentContext: NSManagedObjectContext
let context: NSManagedObjectContext
/// In Core Data, I can create a child context from a background context.
/// This lets you modify the context and save it without updating the main context.
init(progress: Progress = Progress()) {
parentContext = CoreDataStack.shared.newBackgroundContext()
let childContext = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
childContext.parent = parentContext
self.context = childContext
}
/// To commit changes, save the parent context pushing them to the main context.
func commitChange() async throws {
// ERROR: Sending 'self.parentContext' risks causing data races
try await parentContext.perform {
try self.parentContext.save()
}
}
func makeChanges() async throws {
// Do unrelated expensive tasks on the child context...
// As with the Swift Data example, I am unable to create a service that uses the current actors context from here.
// ERROR: Sending 'self.context' risks causing data races
let service = ItemService(context: self.context)
}
}
Am I going about this wrong, or is there a solution to fix these errors?
Some services are very large and have their own internal state. So it would be very difficult to merge all of them into a single service. I also am using Core Data, and SwiftData extensively so I need a solution for both.
I seem to have trapped myself into a corner trying to make everything concurrency save, so any help would be appreciated!
I have the following lines of code to access data through CoreData.
import Foundation
import CoreData
import CloudKit
class CoreDataManager {
static let instance = CoreDataManager()
let container: NSPersistentCloudKitContainer
let context: NSManagedObjectContext
init() {
container = NSPersistentCloudKitContainer(name: "ABC")
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
print(error.userInfo)
}
})
context = container.viewContext
context.automaticallyMergesChangesFromParent = true
context.mergePolicy = NSMergePolicy(merge: .mergeByPropertyObjectTrumpMergePolicyType)
}
func save() {
do {
try container.viewContext.save()
print("Saved successfully")
} catch {
print("Error in saving data: \(error.localizedDescription)")
}
}
}
I have confirmed that I can share data between iPhone and iPad. Now, I need to use AppGroup as well. I have changed my code as follows.
import Foundation
import CoreData
import CloudKit
class CoreDataManager {
static let shared = CoreDataManager()
let container: NSPersistentContainer
let context: NSManagedObjectContext
init() {
container = NSPersistentCloudKitContainer(name: "ABC")
container.persistentStoreDescriptions = [NSPersistentStoreDescription(url: FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: "some group name")!.appendingPathComponent("CoreDataMama.sqlite"))]
container.loadPersistentStores(completionHandler: { (description, error) in
if let error = error as NSError? {
print("Unresolved error \(error), \(error.userInfo)")
}
})
context = container.viewContext
context.automaticallyMergesChangesFromParent = true
context.mergePolicy = NSMergePolicy(merge: .mergeByPropertyObjectTrumpMergePolicyType)
}
func save() {
do {
try container.viewContext.save()
print("Saved successfully")
} catch {
print("Error in saving data: \(error.localizedDescription)")
}
}
}
Other files being unaltered, my sample apps aren't sharing data. What am I doing wrong? Just FYI, I'm using actual devices. Thank you for your reading this topic.
Hello,
I have an asset pack that I'm use to periodically distribute a sqlite database thats being used to an NSPersistentStore.
Because the database is over a few GBs, and the files in an AssetPack are not mutable, I have to stream the database into a temporary file, then replace my NSPersistentStore.
This requires that the user has 3x the storage available of the database, and permanently uses twice to storage needed.
I'd like:
To be able to mark a URL/File to be accessible for read/write access
To be able to mark a file / URL as consumed when it's no needed. So that it can be cleared from the user storage while still maintaining an active subscription to the asset pack for updates.
Thank you
Topic:
App & System Services
SubTopic:
iCloud & Data
Tags:
Files and Storage
On demand resources
Core Data
Background Assets
I have a very simple CoreData model that has 1 entity and 2 attributes.
This code works fine:
.onChange(of: searchText) { _, text in
evnts.nsPredicate = text.isEmpty ? nil :NSPredicate(format: "eventName CONTAINS %@ " , text )
but I'd like to also search with the same text string for my second attribute (which is a Date). I believe an OR is appropriate for two conditions (find either one). See attempted code below:
evnts.nsPredicate = text.isEmpty ? nil : NSPredicate(format: "(eventName CONTAINS %@) OR (dueDate CONTAINS %i) " , text )
This crashes immediately %@ does the same. Is there a way to accomplish this?
How is SwiftUI not an option below?