In a document based SwiftData app for macOS, how do you go about opening a (modal) child window connected to the ModelContainer of the currently open document?
Using .sheet() does not really result in a good UX, as the appearing view lacks the standard window toolbar.
Using a separate WindowGroup with an argument would achieve the desired UX. However, as WindowGroup arguments need to be Hashable and Codable, there is no way to pass a ModelContainer or a ModelContext there:
WindowGroup(id: "myWindowGroup", for: MyWindowGroupArguments.self) { $args in
ViewThatOpensInAWindow(args: args)
}
Is there any other way?
SwiftData
RSS for tagSwiftData is an all-new framework for managing data within your apps. Models are described using regular Swift code, without the need for custom editors.
Posts under SwiftData tag
200 Posts
Sort by:
Post
Replies
Boosts
Views
Activity
Here’s the situation:
• You’re downloading a huge list of data from iCloud.
• You’re saving it one by one (sequentially) into SwiftData.
• You don’t want the SwiftUI view to refresh until all the data is imported.
• After all the import is finished, SwiftUI should show the new data.
The Problem
If you insert into the same ModelContext that SwiftUI’s @Environment(.modelContext) is watching, each insert may cause SwiftUI to start reloading immediately.
That will make the UI feel slow, and glitchy, because SwiftUI will keep trying to re-render while you’re still importing.
How to achieve this in Swift Data ?
I have a document based SwiftData app in which I would like to implement a persistent cache. For obvious reasons, I would not like to store the contents of the cache in the documents themselves, but in my app's data directory.
Is a use case, in which a document based SwiftData app uses not only the ModelContainers from the currently open files, but also a ModelContainer writing a database file in the app's documents directory (for cache, settings, etc.) supported?
If yes, how can you inject two different ModelContexts, one tied to the currently open file and one tied to the local database, into a SwiftUI view?
Hi,
I am currently developing a document-based application with additional WindowGroup for macOS and have encountered a challenge related to document container management. Specifically, I need to open a windowGroup that shares the same container as the one used in the DocumentGroup. However, my current approach of using a global shared model container has led to unintended behavior: any new document created is linked to existing ones, and changes made in one document are reflected across all documents.
To address this issue, I am looking for a solution that allows each newly created document to be individualized while still sharing the document container with all relevant WindowGroups that require access to the data it holds. I would greatly appreciate any insights or recommendations you might have on how to achieve this.
struct Todo: App {
var body: some Scene {
DocumentGroup(editing: Item.self, contentType: .item) {
ContentView()
}
WindowGroup(for: Item.self) { $item in
ItemView(item:$item)
.modelContainer(Of DocumentGroup above)
}
}
}
Thank you for your time and assistance.
Best regards,
Hi,
I am currently developing a document-based application for macOS and have encountered a challenge related to document container management. Specifically, I need to open a windowGroup that shares the same container as the one used in the DocumentGroup. However, my current approach of using a global shared model container has led to unintended behavior: any new document created is linked to existing ones, and changes made in one document are reflected across all documents.
To address this issue, I am looking for a solution that allows each newly created document to be individualized while still sharing the document container with all relevant WindowGroups that require access to the data it holds. I would greatly appreciate any insights or recommendations you might have on how to achieve this.
Thank you for your time and assistance.
Best regards,
Something like:
@main
struct Todo: App {
var body: some Scene {
DocumentGroup(editing: Item.self, contentType: .item) {
ContentView()
}
WindowGroup {
UndockView()
.modelContainer(of documentGroup above)
}
}
}
Hello,
I am building a pretty large database (~40MB) to be used in my SwiftData iOS app as read-only.
While inserting and updating the data, I noticed a substantial increase in size (+ ~10MB).
A little digging pointed to ACHANGE and ATRANSACTION tables that apparently are dealing with Persistent History Tracking.
While I do appreciate the benefits of that, I prefer to save space.
Could you please point me in the right direction?
Hi, would it be possible that instead of crashing when calling fetchHistory that function simply throws an error instead?
fetchHistory seems to crash when it cannot understand the models if they are not compatible etc… which is understandable, but it makes it really difficult to handle and debug, there's not a lot of details, and honestly I would just rather that it throws an error and let me ignore a history entry that might be useless rather than crashing the entire app.
Thank you!
I have made a Swift App for MacOS 15 under XCode 16.3, which runs fine. I also want to run it under the previous MacOS 14. Unfortunately it crashes without even starting up (it does not even reach the first log output statement on the first view)
The crash reason is
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Exception Type: EXC_BAD_INSTRUCTION (SIGILL)
Exception Codes: 0x0000000000000001, 0x0000000000000000
Termination Reason: Namespace SIGNAL, Code 4 Illegal instruction: 4
Terminating Process: exc handler [2970]
I have set the miminium deployment to MacOS 14.0 but to no effect. The XCode machine is a MacOS 15.4 on Arm M3 and the target machine is MacOS 14.7.5 on Intel (MacBook Air)
I think it might be related to the compiler and linker settings.
I have an issue in my app, where the crashing frame is an assertionFailure in BackingData.set inside SwiftData framework. My own app doesn't appear until frame 14. I have no idea what causes this, or even how to create a reproducible project as this only happens on some devices.
The frame prior to the assertionFailure is this:
#1 (null) in BackingData.set(any:value:) ()
It seems like there is a backing data encoding happening in my Model class, and some value is causing it to fail. The model being accessed is through a relationship, and the frame in the app crashing is along the lines of
Text(parent.child.name)
Obviously, something is wrong in how I have made child, but the part that stand out to me is the assertionFailure in a release build
I'm a first time developer for Swift, (getting on a bit!) but after programming in VB back in the late 90s I wanted to write an app for iPhone. I think I might have gone about it the wrong way, but I've got an app that works great on my iPhone or works great on my iPad. It saves the data persistently on device, but, no matter how much I try, what I read and even resorting to AI (ChatGPT & Gemini) I still can't get it to save the data on iCloud to synchronise between the two and work across the devices. I think it must be something pretty fundamental I'm doing (or more likely not doing) that is causing the issue.
I'm setting up my signing and capabilities as per the available instructions but I always get a fatal error. I think it might be something to do with making fields optional, but at this point I'm second guessing myself and feeling a complete failure. Any advice or pointers would be really gratefully appreciated. I like my app and would like eventually to get it on the App Store but at this point in time I feel it should be on the failed projects heap!
I've even tried a new Xcode project for iOS and asking it to use SwiftData and CloudKit - the default project should work - right? But it absolutely doesn't for me. Please send help!!
I am working with SwiftData and get the below error. I can't find any documentation on it to see what to fix. Any help would be appreciated.
Fatal error: This relationship already has a value but it's not the target:
I'm developing a medication scheduling app similar to Apple Health's Medications feature, and I'd like some input on my current approach to background tasks.
In my app, when a user creates a medication, I generate ScheduledDose objects (with corresponding local notifications) for the next 2 weeks and save them to SwiftData. To ensure this 2-week window stays current, I've implemented a BGAppRefreshTask that runs daily to generate new doses as needed.
My concern is whether BGAppRefreshTask is the appropriate mechanism for this purpose. Since I'm not making any network requests but rather generating and storing local data, I'm questioning if this is the right approach.
I'm also wondering how Apple Health's Medications feature handles this kind of scheduling. Their app seems to maintain future doses regardless of app usage patterns.
Has anyone implemented something similar or can suggest the best background execution API for this type of scenario?
Thanks for any guidance you can provide.
Topic:
App & System Services
SubTopic:
Processes & Concurrency
Tags:
HealthKit
SwiftUI
Background Tasks
SwiftData
I’m trying to build a CRUD app using SwiftData, @Query model and multidatepicker.
The data from a multidatepicker is stored or persists in SwiftData as Set = [].
My current dilemma is how to use SwiftData and @Query model Predicate to find all records on the current date.
I can’t find any SwiftData documentation or examples @Query using Set = [].
My CRUD app should retrieve all records for the current date. Unfortunately, I don’t know the correct @Query model syntax for Set = [].
Definitely one of the stranger quirks of SwiftData I've come across.
I have a ScriptView that shows Line entities related to a Production, and a TextEnterScriptView that’s presented in a sheet to input text.
I’m noticing that every time I type in the TextEditor within TextEnterScriptView, a new Line shows up in ScriptView — even though I haven’t explicitly inserted it into the modelContext.
I'm quite confused because even though I’m only assigning a new Line to a local @State array in TextEnterScriptView, every keystroke in the TextEditor causes a duplicate Line to appear in ScriptView.
In other words, Why is SwiftData creating new Line entities every time I type in the TextEditor, even though I’m only assigning to a local @State array and not explicitly inserting them into the modelContext?
Here is my minimal reproducible example:
import SwiftData
import SwiftUI
@main
struct testApp: App {
var body: some Scene {
WindowGroup {
ContentView()
.modelContainer(for: Line.self, isAutosaveEnabled: false)
}
}
}
struct ContentView: View {
@Environment(\.modelContext) var modelContext
@Query(sort: \Production.title) var productions: [Production]
var body: some View {
NavigationStack {
List(productions) { production in
NavigationLink(value: production) {
Text(production.title)
}
}
.navigationDestination(for: Production.self) { production in
ScriptView(production: production)
}
.toolbar {
Button("Add", systemImage: "plus") {
let production = Production(title: "Test \(productions.count + 1)")
modelContext.insert(production)
do {
try modelContext.save()
} catch {
print(error)
}
}
}
.navigationTitle("Productions")
}
}
}
struct ScriptView: View {
@Query private var lines: [Line]
let production: Production
@State private var isShowingSheet: Bool = false
var body: some View {
List {
ForEach(lines) { line in
Text(line.content)
}
}
.toolbar {
Button("Show Sheet") {
isShowingSheet.toggle()
}
}
.sheet(isPresented: $isShowingSheet) {
TextEnterScriptView(production: production)
}
}
}
struct TextEnterScriptView: View {
@Environment(\.dismiss) var dismiss
@State private var text = ""
@State private var lines: [Line] = []
let production: Production
var body: some View {
NavigationStack {
TextEditor(text: $text)
.onChange(of: text, initial: false) {
lines = [Line(content: "test line", production: production)]
}
.toolbar {
Button("Done") {
dismiss()
}
}
}
}
}
@Model
class Production {
@Attribute(.unique) var title: String
@Relationship(deleteRule: .cascade, inverse: \Line.production)
var lines: [Line] = []
init(title: String) {
self.title = title
}
}
@Model
class Line {
var content: String
var production: Production?
init(content: String, production: Production?) {
self.content = content
self.production = production
}
}
Context:
The SwiftUI @Query macro has an internal modelContext.
The ModelActor also has a modelContext, from which the data should be read/written.
Issue:
When writing to @Model data fetched with @Query macro using a ModelActor, it will crash in the most not-obvious ways.
Also, fetching @Model with ModelActor will result in errors in Swift 6 since @Model aren't sendable.
Problem to Solve:
- How to write a good amount of data to SwiftData/CoreData without blocking the UI thread?
Would the recommendation from the Apple team be that a large amount of data should be read/written with ModelActor and a small amount should be done with the @Query's internal modelContext ?
The following complex migration consistently crashes the app with the following error:
SwiftData/PersistentModel.swift:726: Fatal error: What kind of backing data is this? SwiftData._KKMDBackingData<SwiftDataMigration.ItemSchemaV1.ItemList>
My app relies on a complex migration that involves these optional 1 to n relationships. Theoretically I could not assign the relationships in the willMigrate block but afterwards I am not able to tell which list and items belonged together.
Steps to reproduce:
Run project
Change typealias CurrentSchema to ItemSchemaV2 instead of ItemSchemaV1.
Run project again -> App crashes
My setup:
Xcode Version 16.2 (16C5032a)
MacOS Sequoia 15.4
iPhone 12 with 18.3.2 (22D82)
Am I doing something wrong or did I stumble upon a bug? I have a demo Xcode project ready but I could not upload it here so I put the code below.
Thanks for your help
typealias CurrentSchema = ItemSchemaV1
typealias ItemList = CurrentSchema.ItemList
typealias Item = CurrentSchema.Item
@main
struct SwiftDataMigrationApp: App {
var sharedModelContainer: ModelContainer = {
do {
return try ModelContainer(for: ItemList.self, migrationPlan: MigrationPlan.self)
} catch {
fatalError("Could not create ModelContainer: \(error)")
}
}()
var body: some Scene {
WindowGroup {
ContentView()
}
.modelContainer(sharedModelContainer)
}
}
This is the migration plan
enum MigrationPlan: SchemaMigrationPlan {
static var schemas: [any VersionedSchema.Type] {
[ItemSchemaV1.self, ItemSchemaV2.self]
}
static var stages: [MigrationStage] = [
MigrationStage.custom(fromVersion: ItemSchemaV1.self, toVersion: ItemSchemaV2.self, willMigrate: { context in
print("Started migration")
let oldlistItems = try context.fetch(FetchDescriptor<ItemSchemaV1.ItemList>())
for list in oldlistItems {
let items = list.items.map { ItemSchemaV2.Item(timestamp: $0.timestamp)}
let newList = ItemSchemaV2.ItemList(items: items, name: list.name, note: "This is a new property")
context.insert(newList)
context.delete(list)
}
try context.save() // Crash indicated here
print("Finished willMigrate")
}, didMigrate: { context in
print("Did migrate successfully")
})
]
}
The versioned schemas
enum ItemSchemaV1: VersionedSchema {
static var versionIdentifier = Schema.Version(1, 0, 0)
static var models: [any PersistentModel.Type] {
[Item.self]
}
@Model
final class Item {
var timestamp: Date
var list: ItemSchemaV1.ItemList?
init(timestamp: Date) {
self.timestamp = timestamp
}
}
@Model
final class ItemList {
@Relationship(deleteRule: .cascade, inverse: \ItemSchemaV1.Item.list)
var items: [Item]
var name: String
init(items: [Item], name: String) {
self.items = items
self.name = name
}
}
}
enum ItemSchemaV2: VersionedSchema {
static var versionIdentifier = Schema.Version(2, 0, 0)
static var models: [any PersistentModel.Type] {
[Item.self]
}
@Model
final class Item {
var timestamp: Date
var list: ItemSchemaV2.ItemList?
init(timestamp: Date) {
self.timestamp = timestamp
}
}
@Model
final class ItemList {
@Relationship(deleteRule: .cascade, inverse: \ItemSchemaV2.Item.list)
var items: [Item]
var name: String
var note: String
init(items: [Item], name: String, note: String = "") {
self.items = items
self.name = name
self.note = note
}
}
}
Last the ContentView:
struct ContentView: View {
@Query private var itemLists: [ItemList]
var body: some View {
NavigationSplitView {
List {
ForEach(itemLists) { list in
NavigationLink {
List(list.items) { item in
Text(item.timestamp.formatted(date: .abbreviated, time: .complete))
}
.navigationTitle(list.name)
} label: {
Text(list.name)
}
}
}
.navigationTitle("Crashing migration demo")
.onAppear {
if itemLists.isEmpty {
for index in 0..<10 {
let items = [Item(timestamp: Date.now)]
let listItem = ItemList(items: items, name: "List No. \(index)")
modelContext.insert(listItem)
}
try! modelContext.save()
}
}
} detail: {
Text("Select an item")
}
}
}
I've noticed that SwiftData's @Relationship seems to potentially cause application crashes.
The crash error is shown in the image.
Since this crash appears to be random and I cannot reproduce it under specific circumstances, I can only temporarily highlight that this issue seems to exist.
@Model final class TrainInfo {
@Relationship(deleteRule: .cascade, inverse: \StopStation.trainInfo)
var stations: [StopStation]?
}
@Model final class StopStation {
@Relationship
var trainInfo: TrainInfo?
}
/// some View
var origin: StopStationDisplayable? {
if let train = train as? TrainInfo {
return train.stations?.first(where: { $0.isOrigin }) ?? train.stations?.first(where: { $0.isStarting })
}
return nil
}
// Some other function or property
func someFunction() {
if let origin, let destination {
// Function implementation
}
}
If use a SortDescriptor for a model and sort by some attribute from a relationship, in DEBUG mode it all works fine and sorts. However, in release mode, it is an instant crash.
SortDescriptor(.name, order: .reverse) ---- works
SortDescriptor(.assignedUser?.name, order: .reverse) ---- works in debug but crash in release.
What is the issue here, is it that SwiftData just incompetent to do this?
Setup
I am running a versionedSchema for my SwiftData model and attempting a migration. The new version contains a new attribute, with a type of a new custom enum defined in the @Model class, a default value, and a private(set). Migration was completed with a migrationPlan with nil values for willMigrate and didMigrate.
Example - Previous Version
@Model
class MyNumber {
var num: Int
init() {
// Init Code
}
}
Example - Newest Version
@Model
class MyNumber {
var num: Int
private(set) var rounding: RoundAmount = MyNumber.RoundAmount.thirtyMinute
init() {
// Init Code
}
enum RoundAmount {
case fiveMinute, tenMinute, thirtyMinute
}
}
Issue
Running this code, I get a swiftData error for “SwiftData/ModelCoders.swift:1585: nil value passed for a non-optional keyPath, /MyNumber.rounding”
I assume this means a failure of the swiftData lightweight migration? I have reverted the version, removed private(set) and re-tried the migration with no success.
Using the versionedSchema with migrationPlans, are lightweight migrations possible? Could this be an issue with the use of a custom enum? Other changes in my actual project migrated successfully so I’m lost on why I’m having this issue.
Hi there, I got two models here:
Two Models, with Many-To-Many Relationship
@Model
final class PresetParams: Identifiable {
@Attribute(.unique) var id: UUID = UUID()
var positionX: Float = 0.0
var positionY: Float = 0.0
var positionZ: Float = 0.0
var volume: Float = 1.0
@Relationship(deleteRule: .nullify, inverse: \Preset.presetAudioParams)
var preset = [Preset]()
init(position: SIMD3<Float>, volume: Float) {
self.positionX = position.x
self.positionY = position.y
self.positionZ = position.z
self.volume = volume
self.preset = []
}
var position: SIMD3<Float> {
get {
return SIMD3<Float>(x: positionX, y: positionY, z: positionZ)
}
set {
positionX = newValue.x
positionY = newValue.y
positionZ = newValue.z
}
}
}
@Model
final class Preset: Identifiable {
@Attribute(.unique) var id: UUID = UUID()
var presetName: String
var presetDesc: String?
var presetAudioParams = [PresetParams]() // Many-To-Many Relationship.
init(presetName: String, presetDesc: String? = nil) {
self.presetName = presetName
self.presetDesc = presetDesc
self.presetAudioParams = []
}
}
To be honest, I don't fully understand how the @Relationship thing works properly in a Many-To-Many relationship situation. Some tutorials suggest that it's required on the "One" side of an One-To-Many Relationship, while the "Many" side doesn't need it.
And then there is an ObservableObject called "ModelActors" to manage all ModelActors, ModelContainer, etc.
ModelActors, ModelContainer...
class ModelActors: ObservableObject {
static let shared: ModelActors = ModelActors()
let sharedModelContainer: ModelContainer
private init() {
var schema = Schema([
// ...
Preset.self,
PresetParams.self,
// ...
])
do {
sharedModelContainer = try ModelContainer(for: schema, migrationPlan: MigrationPlan.self)
} catch {
fatalError("Could not create ModelContainer: \(error.localizedDescription)")
}
}
}
And there is a migrationPlan:
MigrationPlan
// MARK: V102
// typealias ...
// MARK: V101
typealias Preset = AppSchemaV101.Preset
typealias PresetParams = AppSchemaV101.PresetParams
// MARK: V100
// typealias ...
enum MigrationPlan: SchemaMigrationPlan {
static var schemas: [VersionedSchema.Type] {
[
AppSchemaV100.self,
AppSchemaV101.self,
AppSchemaV102.self,
]
}
static var stages: [MigrationStage] {
[AppMigrateV100toV101, AppMigrateV101toV102]
}
static let AppMigrateV100toV101 = MigrationStage.lightweight(fromVersion: AppSchemaV100.self, toVersion: AppSchemaV101.self)
static let AppMigrateV101toV102 = MigrationStage.lightweight(fromVersion: AppSchemaV101.self, toVersion: AppSchemaV102.self)
}
// MARK: Here is the AppSchemaV101
enum AppSchemaV101: VersionedSchema {
static var versionIdentifier: Schema.Version = Schema.Version(1, 0, 1)
static var models: [any PersistentModel.Type] {
return [ // ...
Preset.self,
PresetParams.self
]
}
}
Fails on iOS 18.3.x: "Failed to fulfill link PendingRelationshipLink"
So I expected the SwiftData subsystem to work correctly with version control. A good news is that on iOS 18.1 it does work. But it fails on iOS 18.3.x with a fatal Error:
"SwiftData/SchemaCoreData.swift:581: Fatal error: Failed to fulfill link PendingRelationshipLink(relationshipDescription: (<NSRelationshipDescription: 0x30377fe80>), name preset, isOptional 0, isTransient 0, entity PresetParams, renamingIdentifier preset, validation predicates (), warnings (), versionHashModifier (null)userInfo {}, destination entity Preset, inverseRelationship (null), minCount 0, maxCount 0, isOrdered 0, deleteRule 1, destinationEntityName: "Preset", inverseRelationshipName: Optional("presetAudioParams")), couldn't find inverse relationship 'Preset.presetAudioParams' in model"
Fails on iOS 17.5: Another Error
I tested it on iOS 17.5 and found another issue: Accessing or mutating the "PresetAudioParams" property causes the SwiftData Macro Codes to crash, affecting both Getter and Setter. It fails with an error:
"EXC_BREAKPOINT (code=1, subcode=0x1cc1698ec)"
Tweaking the @Relationship marker and ModelContainer settings didn't fix the problem.