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