I'm a bit lost because of a problem I never experienced before: I create entries in 3 Core Data tables and link them. As long as the app is open, everything is fine, I can see the database entries in the three tables. Once the App is closed and restarted, however, the new entries in two of the three tables are gone.
I use Core Data for data storage and DB Browser for SQLite for inspecting the database running in the Simulator.
Here's the relevant function where all Core Data handling happens:
/**
Creates a new ComposedFoodItem from the ComposedFoodItemViewModel.
Creates the related FoodItem and the Ingredients.
Creates all relationships.
- Parameter composedFoodItemVM: The source view model.
- Returns: A Core Data ComposedFoodItem; nil if there are no Ingredients.
*/
static func create(from composedFoodItemVM: ComposedFoodItemViewModel, generateTypicalAmounts: Bool) -> ComposedFoodItem? {
debugPrint(AppDelegate.persistentContainer.persistentStoreDescriptions) // The location of the .sqlite file
let moc = AppDelegate.viewContext
// Create new ComposedFoodItem (1)
let cdComposedFoodItem = ComposedFoodItem(context: moc)
// No existing composed food item, therefore create a new UUID
cdComposedFoodItem.id = UUID()
// Fill data
cdComposedFoodItem.amount = Int64(composedFoodItemVM.amount)
cdComposedFoodItem.numberOfPortions = Int16(composedFoodItemVM.numberOfPortions)
// Create the related FoodItem (2)
let cdFoodItem = FoodItem.create(from: composedFoodItemVM, generateTypicalAmounts: generateTypicalAmounts)
// Relate both (3)
cdComposedFoodItem.foodItem = cdFoodItem
// Add cdComposedFoodItem to composedFoodItemVM
composedFoodItemVM.cdComposedFoodItem = cdComposedFoodItem
// Add new ingredients (4)
if let cdIngredients = Ingredient.create(from: composedFoodItemVM) {
cdComposedFoodItem.addToIngredients(NSSet(array: cdIngredients))
// Save new composed food item
try? moc.save()
// Return the ComposedFoodItem
return cdComposedFoodItem
} else {
// There are no ingredients, therefore we delete it again and return nil
moc.delete(cdComposedFoodItem)
try? moc.save()
return nil
}
}
What the function does:
Creates a new entry in table ComposedFoodItem
Creates another new entry in another table FoodItem
Relates both entries
Creates another 1..n entries in a third table Ingredient and links these to the entry created in step 1
All this works fine, I can see all relations and entries in the database.
Then I quit and restart the app. The entry created in step 2 is still there, but the entries created in steps 1 and 4 are gone, as well as the relationships (of course).
My suspicion: I recently implemented a Core Data migration from Data Model version 1 ("EasyFPU") to version 2 ("EasyFPU 2"). In this migration, I have two custom migration policies for exactly the two tables, which are not stored. The migration policies are pretty simple (and identical for both tables):
/**
No Ingredient is created in the destination model, i.e., there will be no Ingredients
*/
override func createDestinationInstances(forSource sourceIngredient: NSManagedObject, in mapping: NSEntityMapping, manager: NSMigrationManager) throws {
// Do nothing on purpose
debugPrint("Not migrating Ingredient with ID: \((sourceIngredient as? Ingredient)?.id.uuidString ?? "unknown")")
}
And what I suspect is, that this migration policies are somehow called when restarting the app, but I have no idea why, because the migration has already happened before. If I set a breakpoint in the debugPrint line of the code snippet above, I actually never reach this breakpoint - as expected. Nevertheless are the two tables Ingredient and ComposedFoodItem empty after restart.
My AppDelegate Core Data persistentContainer variable looks like this:
lazy var persistentContainer: NSPersistentCloudKitContainer = {
let container = NSPersistentCloudKitContainer(name: "EasyFPU")
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
return container
}()
I tried to replace "EasyFPU" with "EasyFPU 2", but this apparently is not the version, but the container name.
Any idea? Thanks in advance!
