iOS 18 strange SwiftData fatal error

The error seems to be the same as what was discussed in the iOS 18 SwiftData ModelContext reset post. You might take a look to see if that helps.

The error typically happens when you try to access a model instance after the associated model container is (unintentionally) released. You can review your code to see if that is your case, and if yes, avoid that.

Best,
——
Ziqiao Chen
 Worldwide Developer Relations.

I can confirm that changing the code I replied with earlier, to the following code fixes the problem:

var modelContainer: ModelContainer?
    init() {
        self.modelContainer = try? ModelContainer(for: Event.self)
    }
    @MainActor
    func fetchEvents() -> [Event] {
        guard let modelContainer = modelContainer else {
            return []
        }
        
        let descriptor = FetchDescriptor<Event>(sortBy: [SortDescriptor(\.dateCreated, order: .reverse)])
        guard let events = try? modelContainer.mainContext.fetch(descriptor) else {
            return []
        }
        
        return events
    }

Yeah, the code you provided in your comment creates the model container and holds it with a local variable, which is released after fetchEvents is done, which triggers the error when you try to access the events.

Your new code seems to hold the model container with a member variable, whose life cycle is the same as the object that owns the variable. In case you don't release the object, the model container will be there.

Best,
——
Ziqiao Chen
 Worldwide Developer Relations.