Which versions of iOS does this target?

This skill is optimized for iOS 17 and above, with specific considerations for features and bugs found in the early SwiftData releases.

How does this skill handle property type changes?

It implements a two-stage migration pattern using an intermediate schema that contains both old and new property types to safely transform data.

What is the main limitation of SwiftData migrations?

SwiftData's willMigrate closure only sees the old schema, while didMigrate only sees the new one, preventing direct data transfer between versions in a single step.

Does this support many-to-many relationships?

Yes, it provides specific guidance on explicit inverse relationships and array requirements needed to preserve many-to-many links during migration.

SwiftData Migration Expert

Name: SwiftData Migration Expert
Author: CharlesWiltgen

byCharlesWiltgen

•

233

Mobile Development

Implements complex SwiftData schema migrations using two-stage patterns to overcome model versioning limitations.

About

This skill provides a specialized framework for managing SwiftData migrations that exceed the capabilities of automatic lightweight updates. It addresses the critical architectural constraint where SwiftData's migration closures cannot access old and new models simultaneously. By utilizing VersionedSchema and SchemaMigrationPlan patterns, the skill enables developers to safely perform property type changes, preserve complex relationships, and execute data transformations while ensuring data integrity across iOS, iPadOS, and watchOS apps.

Key Features

Two-stage migration patterns for property type transformations
233 GitHub stars
Complete VersionedSchema snapshot implementation guidance
Workarounds for iOS 17+ SwiftData relationship bugs
Preservation of one-to-many and many-to-many relationships
Prefetching strategies to maintain data links during migration

Use Cases

Changing a property from String to AttributedString without data loss
Migrating many-to-many relationships with explicit inverse requirements
Converting optional properties to required properties with default population

About

Key Features

Two-stage migration patterns for property type transformations
233 GitHub stars
Complete VersionedSchema snapshot implementation guidance
Workarounds for iOS 17+ SwiftData relationship bugs
Preservation of one-to-many and many-to-many relationships
Prefetching strategies to maintain data links during migration

Use Cases

Changing a property from String to AttributedString without data loss
Migrating many-to-many relationships with explicit inverse requirements
Converting optional properties to required properties with default population