SwiftData: Solving data persistence on disk

After watching the WWDC2023 presentation of SwiftData, I decided to try it.

I wanted to persist my model’s data between relaunches but I couldn’t make it work. The autosave feature didn’t work as expected. Based on the documentation, this feature is activated by default.

After a few hours, I discovered that the option isAutosaveEnabled of a ModelContainer is only set to true when you don’t instance a ModelContainer yourself.

// Here I create a ModelContainer for the Boat model.
@MainActor
let container: ModelContainer = {
    do {
        let container = try ModelContainer(
            for: Boat.self, ModelConfiguration()
        )
        return container
    } catch {
        fatalError("Failed to create container")
    }
}()

// And I pass it to my view
@main
struct OnshoreApp: App {

    var body: some Scene {
            WindowGroup {
                ContentView()
            .modelContainer(container)
        }
    }
}

In this case, the isAutosaveEnabled is set to false.

But if I write this:

@main
struct OnshoreApp: App {

    var body: some Scene {
            WindowGroup {
                ContentView()
            .modelContainer(for: Boat.self)
        }
    }
}

Now the isAutosaveEnabled is set to true!

I only found out by watching Dive deeper into SwiftData (timestamps 11:00).