I'm currently syncing core data with the CloudKit private and public databases, as you can see in the code below, I'm saving the private database in the default configuration in Core Data and the public in a configuration called Public everything works fine when NSPersistentCloudKitContainer syncs, what I'm having an issue with is trying to save to the public data store PublicStore, for instance when I try to save with func createIconImage(imageName: String) it saves the image to the "default" store, not the PublicStore(Public configuration).
What could I do to make the createIconImage() function save to the PublicStore sqlite database?
class CoreDataManager: ObservableObject{
static let instance = CoreDataManager()
private let queue = DispatchQueue(label: "CoreDataManagerQueue")
@AppStorage(UserDefaults.Keys.iCloudSyncKey) private var iCloudSync = false
lazy var context: NSManagedObjectContext = {
return container.viewContext
}()
lazy var container: NSPersistentContainer = {
return setupContainer()
}()
init(inMemory: Bool = false){
if inMemory {
container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
}
}
func updateCloudKitContainer() {
queue.sync {
container = setupContainer()
}
}
private func getDocumentsDirectory() -> URL {
return FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
}
private func getStoreURL(for storeName: String) -> URL {
return getDocumentsDirectory().appendingPathComponent("\(storeName).sqlite")
}
func setupContainer()->NSPersistentContainer{
let container = NSPersistentCloudKitContainer(name: "CoreDataContainer")
let cloudKitContainerIdentifier = "iCloud.com.example.MyAppName"
guard let description = container.persistentStoreDescriptions.first else{
fatalError("###\(#function): Failed to retrieve a persistent store description.")
}
description.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
description.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
if iCloudSync{
if description.cloudKitContainerOptions == nil {
let options = NSPersistentCloudKitContainerOptions(containerIdentifier: cloudKitContainerIdentifier)
description.cloudKitContainerOptions = options
}
}else{
print("Turning iCloud Sync OFF... ")
description.cloudKitContainerOptions = nil
}
// Setup public database
let publicDescription = NSPersistentStoreDescription(url: getStoreURL(for: "PublicStore"))
publicDescription.configuration = "Public" // this is the configuration name
if publicDescription.cloudKitContainerOptions == nil {
let publicOptions = NSPersistentCloudKitContainerOptions(containerIdentifier: cloudKitContainerIdentifier)
publicOptions.databaseScope = .public
publicDescription.cloudKitContainerOptions = publicOptions
}
container.persistentStoreDescriptions.append(publicDescription)
container.loadPersistentStores { (description, error) in
if let error = error{
print("Error loading Core Data. \(error)")
}
}
container.viewContext.automaticallyMergesChangesFromParent = true
container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
return container
}
func save(){
do{
try context.save()
//print("Saved successfully!")
}catch let error{
print("Error saving Core Data. \(error.localizedDescription)")
}
}
}
class PublicViewModel: ObservableObject {
let manager: CoreDataManager
@Published var publicIcons: [PublicServiceIconImage] = []
init(coreDataManager: CoreDataManager = .instance) {
self.manager = coreDataManager
}
func createIconImage(imageName: String) {
let newImage = PublicServiceIconImage(context: manager.context)
newImage.imageName = imageName
newImage.id = UUID()
save()
}
func save() {
self.manager.save()
}
}
After days of trying different things, I accidentally found out that the order of descriptions in the container array plays a crucial role in how Core Data prioritizes loading configurations and saving entities. In my original code, I was loading the default configuration first as shown below...
guard let description = container.persistentStoreDescriptions.first else{
fatalError("###\(#function): Failed to retrieve a persistent store description.")
}
Then I was appending the public configuration as follows...
container.persistentStoreDescriptions.append(publicDescription)
Leaving the public configuration at the end of the persistentStoreDescriptions array, and apparently, the way Core Data works is that it searches the first configuration, and if the entity you're saving exists in the first configuration, it saves it in that configuration otherwise it keeps looping through all configs until it finds the entity in one of the configurations but since (by default) the Default configuration contains all entities, it was always saving to the default configuration so, the solution is to always leave the default configuration as the last item in the array.
Here is what I did that solved my issue:
Replaced this line...
container.persistentStoreDescriptions.append(publicDescription)
with...
container.persistentStoreDescriptions = [publicDescription, description]
Again, I basically added the Public configuration to the first configuration in the array. The key here is to always leave the default configuration at last, regardless of how many configurations you have.
FYI - The sample project from the Linking Data Between two Core Data Stores led me to try to reorder the configurations in the array.
https://developer.apple.com/documentation/coredata/linking_data_between_two_core_data_stores