I am trying to create a SwiftData app that has two separate SQLite data stores – one for data I will pre-create and distribute with my app and one for data the user will create when running the app – something like described in this article by Paul Hudson.

When I create and save items I get the error:

Failed to save after place creation: The model configuration used to open the store is incompatible with the one that was used to create the store.

For testing, I have two simple models:

@Model
class Person: Identifiable {
    @Attribute(.unique) let id: UUID
    let name: String
    
    init(id: UUID = UUID(), name: String) {
        self.id = id
        self.name = name
    }
}

@Model
class Place: Identifiable {
    @Attribute(.unique) let id: UUID
    let name: String
    
    init(id: UUID = UUID(), name: String) {
        self.id = id
        self.name = name
    }
}

I initialise SwiftData:

@main
struct MultiStoreApp: App {
    
    var container: ModelContainer
    
    init() {
        let peopleStoreURL = URL.documentsDirectory.appending(path: "people.store")
        let placeStoreURL = URL.documentsDirectory.appending(path: "places.store")
        
        let peopleConfig = ModelConfiguration(schema: Schema([Person.self]), url: peopleStoreURL)
        let placesConfig = ModelConfiguration(schema: Schema([Place.self]), url: placeStoreURL)
        
        do {
            self.container = try ModelContainer(for: Person.self, Place.self, configurations: peopleConfig, placesConfig)
        } catch {
            fatalError("Failed to create model container: (error.localizedDescription)")
        }
    }
    
    var body: some Scene {
        WindowGroup {
            ContentView()
                .modelContainer(container)
        }
    }
}

I then have a simple View that displays a list of all places and people, along with buttons to add people and places.

struct ContentView: View {
    @Environment(.modelContext) private var modelContext
    
    @Query var people: [Person]
    @Query var places: [Place]
    
    var body: some View {
        NavigationStack {
            List {
                Section("People") {
                    ForEach(people) { person in
                        VStack(alignment: .leading) {
                            Text(person.name)
                            Text(person.id.uuidString)
                                .font(.caption)
                        }
                    }
                }
                
                Section("Places") {
                    ForEach(places) { place in
                        VStack(alignment: .leading) {
                            Text(place.name)
                            Text(place.id.uuidString)
                                .font(.caption)
                        }
                    }
                }
            }
            
            GroupBox {
                HStack {
                    Button(action: {
                        let person = Person(name: "Person (people.count)")
                        modelContext.insert(person)
                        do {
                            try modelContext.save()
                        } catch {
                            print("Failed to save after person creation: (error.localizedDescription)")
                        }
                    }, label: {
                        Text("Add Person")
                    })
                    
                    Spacer()
                    
                    Button(action: {
                        let place = Place(name: "Place (places.count)")
                        modelContext.insert(place)
                        do {
                            try modelContext.save()
                        } catch {
                            print("Failed to save after place creation: (error.localizedDescription)")
                        }
                    }, label: {
                        Text("Add Place")
                    })
                }
            }
            .padding()
        }
    }
}

When I run the app on a clean simulator, I can add objects of one type, but as soon as I add an object of the other type I start getting errors.

Is what I’m trying to do possible?