I'm experiencing a critical issue with SwiftData custom migrations where objects created during migration appear to be inserted successfully but aren't persisted or found by queries after migration completes. The migration logs show objects being created, but subsequent queries return zero results.
I'm migrating from schema version V2 to V2_5, which involves:
Renaming Person class to GroupData
Keeping the same data structure but changing the class name while keeping the old class.
Using a custom migration stage to copy data from old to new schema
Below is an extract of my two schema and migration plan:
Environment:
Xcode 16.0,
iOS 18.0,
Swift 6.0
SchemaV2
enum LinkMapV2: VersionedSchema {
static let versionIdentifier: Schema.Version = .init(2, 0, 0)
static var models: [any PersistentModel.Type] {
[AnnotationData.self, Person.self, History.self]
}
@Model
final class Person {
@Attribute(.unique) var id: UUID
var name: String
var photo: String
var requirement: String
var statue: Bool
var annotationId: UUID?
var number: Int = 0
init(id: UUID = UUID(), name: String = "", photo: String = "", requirement: String = "", status: Bool = false, annotationId: UUID? = nil, number: Int = 0) {
self.id = id
self.name = name
self.photo = photo
self.requirement = requirement
self.statue = status
self.annotationId = annotationId
self.number = number
}
}
}
Schema V2_5
static let versionIdentifier: Schema.Version = .init(2, 5, 0)
static var models: [any PersistentModel.Type] {
[AnnotationData.self, Person.self, GroupData.self, History.self]
}
// Keep the old Person model for migration
@Model
final class Person {
@Attribute(.unique) var id: UUID
var name: String
var photo: String
var requirement: String
var statue: Bool
var annotationId: UUID?
var number: Int = 0
init(id: UUID = UUID(), name: String = "", photo: String = "", requirement: String = "", status: Bool = false, annotationId: UUID? = nil, number: Int = 0) {
self.id = id
self.name = name
self.photo = photo
self.requirement = requirement
self.statue = status
self.annotationId = annotationId
self.number = number
}
}
// Add the new GroupData model that mirrors Person
@Model
final class GroupData {
@Attribute(.unique) var id: UUID
var name: String
var photo: String
var requirement: String
var status: Bool
var annotationId: UUID?
var number: Int = 0
init(id: UUID = UUID(), name: String = "", photo: String = "", requirement: String = "", status: Bool = false, annotationId: UUID? = nil, number: Int = 0) {
self.id = id
self.name = name
self.photo = photo
self.requirement = requirement
self.status = status
self.annotationId = annotationId
self.number = number
}
}
}
Migration Plan
static let migrationV2toV2_5 = MigrationStage.custom(
fromVersion: LinkMapV2.self,
toVersion: LinkMapV2_5.self,
willMigrate: { context in
do {
let persons = try context.fetch(FetchDescriptor<LinkMapV2.Person>())
print("=== MIGRATION STARTED ===")
print("Found \(persons.count) Person objects to migrate")
guard !persons.isEmpty else {
print("No Person data requires migration")
return
}
for person in persons {
print("Migrating Person: '\(person.name)' with ID: \(person.id)")
let newGroup = LinkMapV2_5.GroupData(
id: person.id, // Keep the same ID
name: person.name,
photo: person.photo,
requirement: person.requirement,
status: person.statue,
annotationId: person.annotationId,
number: person.number
)
context.insert(newGroup)
print("Inserted new GroupData: '\(newGroup.name)'")
// Don't delete the old Person yet to avoid issues
// context.delete(person)
}
try context.save()
print("=== MIGRATION COMPLETED ===")
print("Successfully migrated \(persons.count) Person objects to GroupData")
} catch {
print("=== MIGRATION ERROR ===")
print("Migration failed with error: \(error)")
}
},
didMigrate: { context in
do {
// Verify migration in didMigrate phase
let groups = try context.fetch(FetchDescriptor<LinkMapV2_5.GroupData>())
let oldPersons = try context.fetch(FetchDescriptor<LinkMapV2_5.Person>())
print("=== MIGRATION VERIFICATION ===")
print("New GroupData count: \(groups.count)")
print("Remaining Person count: \(oldPersons.count)")
// Now delete the old Person objects
for person in oldPersons {
context.delete(person)
}
if !oldPersons.isEmpty {
try context.save()
print("Cleaned up \(oldPersons.count) old Person objects")
}
// Print all migrated groups for debugging
for group in groups {
print("Migrated Group: '\(group.name)', Status: \(group.status), Number: \(group.number)")
}
} catch {
print("Migration verification error: \(error)")
}
}
)
And I've attached console output below:
Console Output