SwiftData Migration Writer
Create migration from UserDefaults to SwiftData:
- Map keys to entity fields
- Write migration method:
func migrateXIfNeeded() async throws {guard!hasMigrated("X") else {return} // Read UserDefaults // Create/update entity // Archive old keys // Mark migrated} - Add to PreferencesStore extension
- Call on first load
- Test data preservation
Use when: Creating SwiftData entities, migrating preferences, data persistence