I have not had any successful Schema Migration with CloudKit so far so I'm trying to do with with just very basic attributes, with multiple Versioned Schemas
This is the code in my App Main
var sharedModelContainer: ModelContainer = {
let schema = Schema(versionedSchema: AppSchemaV4.self)
do {
return try ModelContainer(
for: schema,
migrationPlan: AppMigrationPlan.self,
configurations: ModelConfiguration(cloudKitDatabase: .automatic))
} catch {
fatalError("Could not create ModelContainer: \(error)")
}
}()
var body: some Scene {
WindowGroup {
ItemListView()
}
.modelContainer(sharedModelContainer)
}
And this is the code for my MigrationPlan and VersionedSchemas.
typealias Item = AppSchemaV4.Item3
enum AppMigrationPlan: SchemaMigrationPlan {
static var schemas: [any VersionedSchema.Type] {
[AppSchemaV1.self, AppSchemaV2.self, AppSchemaV3.self, AppSchemaV4.self]
}
static var stages: [MigrationStage] {
[migrateV1toV2, migrateV2toV3, migrateV3toV4]
}
static let migrateV1toV2 = MigrationStage.lightweight(
fromVersion: AppSchemaV1.self,
toVersion: AppSchemaV2.self
)
static let migrateV2toV3 = MigrationStage.lightweight(
fromVersion: AppSchemaV2.self,
toVersion: AppSchemaV3.self
)
static let migrateV3toV4 = MigrationStage.custom(
fromVersion: AppSchemaV3.self,
toVersion: AppSchemaV4.self,
willMigrate: nil,
didMigrate: { context in
// Fetch all Item1 instances
let item1Descriptor = FetchDescriptor<AppSchemaV3.Item1>()
let items1 = try context.fetch(item1Descriptor)
// Fetch all Item2 instances
let item2Descriptor = FetchDescriptor<AppSchemaV3.Item2>()
let items2 = try context.fetch(item2Descriptor)
// Convert Item1 to Item3
for item in items1 {
let newItem = AppSchemaV4.Item3(name: item.name, text: "Migrated from Item1 on \(item.date)")
context.insert(newItem)
}
// Convert Item2 to Item3
for item in items2 {
let newItem = AppSchemaV4.Item3(name: item.name, text: "Migrated from Item2 with value \(item.value)")
context.insert(newItem)
}
try? context.save()
}
)
}
enum AppSchemaV1: VersionedSchema {
static var versionIdentifier: Schema.Version = Schema.Version(1, 0, 0)
static var models: [any PersistentModel.Type] {
[Item1.self]
}
@Model class Item1 {
var name: String = ""
init(name: String) {
self.name = name
}
}
}
enum AppSchemaV2: VersionedSchema {
static var versionIdentifier: Schema.Version = Schema.Version(2, 0, 0)
static var models: [any PersistentModel.Type] {
[Item1.self]
}
@Model class Item1 {
var name: String = ""
var date: Date = Date()
init(name: String) {
self.name = name
self.date = Date()
}
}
}
enum AppSchemaV3: VersionedSchema {
static var versionIdentifier: Schema.Version = Schema.Version(3, 0, 0)
static var models: [any PersistentModel.Type] {
[Item1.self, Item2.self]
}
@Model class Item1 {
var name: String = ""
var date: Date = Date()
init(name: String) {
self.name = name
self.date = Date()
}
}
@Model class Item2 {
var name: String = ""
var value: Int = 0
init(name: String, value: Int) {
self.name = name
self.value = value
}
}
}
enum AppSchemaV4: VersionedSchema {
static var versionIdentifier: Schema.Version = Schema.Version(4, 0, 0)
static var models: [any PersistentModel.Type] {
[Item1.self, Item2.self, Item3.self]
}
@Model class Item1 {
var name: String = ""
var date: Date = Date()
init(name: String) {
self.name = name
self.date = Date()
}
}
@Model class Item2 {
var name: String = ""
var value: Int = 0
init(name: String, value: Int) {
self.name = name
self.value = value
}
}
@Model class Item3 {
var name: String = ""
var text: String = ""
init(name: String, text: String) {
self.name = name
self.text = text
}
}
}
My experiment was:
To create Items for every version of the schema
Updating the typealias along the way to reflect the latest Item version.
Updating the Schema in my ModelContainer to reflect the latest Schema Version.
By AppSchemaV4, I have expected all my Items to be displayed/migrated to Item3, but it does not seem to be the case.
I can only see newly created Item3 records.
My question is, is there something wrong with how I'm doing the migrations? or are migrations not really working with CloudKit right now?
