SwiftData ModelContainer can not be created in iOS 17.4 Beta

I have an app in the app store which is working fine. Some users reported that they have app crashing when they are using iOS 17.4 beta. I could recreate the issue and it is happening when ModelContainer is crerated. This code..

do {
                let configuration = ModelConfiguration(for: MyTodo.self, isStoredInMemoryOnly: false)
                modelContainer = try ModelContainer(for: MyTodo.self, configurations: configuration)

            } catch {
                fatalError("Failed to load model container.\(error)")
            }

is throwing this error message:

Fatal error: Failed to load model container.SwiftDataError(_error: SwiftData.SwiftDataError._Error.loadIssueModelContainer)
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Posted by
mikrasya
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  • My model do not have any @Attribute(.unique) All properties have default values Relationships are marked as optional App is using CloudKit for iCloud syncronization

    A brandnew app with the same model does not have this issue. When I uncheck "CloutKit" in Signing & Capabilities, the app launch normally.

    —
    mikrasya

  • Widget can obtain the data without error/crash from modelContainer using this code:

            guard let modelContainer = try? ModelContainer(for: MyTodo.self) else {
            return []
        }
    —
    mikrasya

  • I have now identified that this issue is happening due to Relationships in my model. My MyToDo has task defined like this:

    @Relationship(deleteRule: .cascade) var tasks: [MyTask]? = []

    and MyTask has reference back as following:

    var todo: MyTodo?

    Both of them are optional as required for CloudKit. This model can be read in iOS 17.3, but in 17.4 beta, it crashes!

    —
    mikrasya
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Accepted Reply

It seems for whatever reason inverse relationship needs to be explicitly defined. Change from this:

@Relationship(deleteRule: .cascade) var tasks: [MyTask]? = []

to

@Relationship(deleteRule: .cascade, inverse: \MyTask.todo) var tasks: [MyTask]? = []

has solved the crash issue. Works both in iOS 17.3 and 17.4.

Posted by
mikrasya
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Replies

It seems for whatever reason inverse relationship needs to be explicitly defined. Change from this:

@Relationship(deleteRule: .cascade) var tasks: [MyTask]? = []

to

@Relationship(deleteRule: .cascade, inverse: \MyTask.todo) var tasks: [MyTask]? = []

has solved the crash issue. Works both in iOS 17.3 and 17.4.

Posted by
mikrasya
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Thanks @mikrasya for documenting this. I have the same problem, but already have inverses set. Removing inverses didn't help either. (I've read that inverses aren't necessary when using iCloud, that they are automatically inferred). 🤷🏼‍♂️

I sent in a question to Developer Tech Support, and will repeat any solution here for you and the other five who've marked your posting with "Same Here".

Posted by
jhokit
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I tried creating a new app, with a new container, using the Xcode 'stock' Item ie; item.timestamp. I tried it in a 17.4 simulator and iPhone with 17/4. Both failed for the same reason as noted by the OP. Fatal error: Could not create ModelContainer: SwiftDataError(_error: SwiftData.SwiftDataError._Error.loadIssueModelContainer). I also have a "Live" App that is not loading because of 17.4. Also... I have played with the relationships as described in the posts above and nothing worked. Again - Apple's stock, stripped down, Items app is failing.???

Update: As for my app... The culprit was that I had added modelContext into the environment using both an @Environment call and .modelContainer on WindowGroup. By the way, this worked prior to 17.4. The solution was to remove : @Environment(.modelContext) private var modelContext.

As for the 'stock app', I discovered that the issue was that timestamp is not marked optional so it fails. Marking it optional? and then providing ?? Date.now values where needed solved the problem.

Posted by
funcmakerDan
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  • Incredible find @funcmakerDan, thank you. Removing @Environment(.modelContext) fixed it for me as well, on iOS 17.4 and visionOS 1.1, and Sonoma 14.4.

    —
    jhokit

  • As for the Xcode template 'timestamp' app, that might be a different issue. Did you set it up to use iCloud? When using iCloud syncing all @Model members must be optional or have a default value, but the Xcode template doesn't do that, and the compiler doesn't catch it. You get a runtime warning when creating the SwiftData structures.

    —
    jhokit
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