axiom-swiftdata-migration

To migrate a SwiftData property type from String to AttributedString, you implement a two-stage migration process using VersionedSchema and SchemaMigrationPlan to safely convert existing data while preserving model integrity.

You need custom SwiftData schema migrations using VersionedSchema when handling complex data transformations like property type changes or relationship restructuring, whereas lightweight migrations only cover simpler automatic changes like adding or renaming properties.

SwiftData custom schema migrations address relationship preservation for one-to-many and many-to-many connections, ensuring that existing data links remain intact and valid when you update your model definitions across versions.

The willMigrate and didMigrate limitation in SwiftData refers to lifecycle constraints during the migration process, requiring developers to adopt two-stage migration patterns to handle complex data transformations safely.

Testing SwiftData schema migrations on real devices requires running the SchemaMigrationPlan on simulators and physical hardware to thoroughly validate data integrity, relationship preservation, and type conversion behavior.

You define multiple versions of a SwiftData model using VersionedSchema to manage schema versioning, allowing your application to track model definitions and execute custom migrations through SchemaMigrationPlan.