iOS Data & Persistence Router

You MUST use this skill for ANY data persistence, database, storage, CloudKit, or serialization work.

When to Use

Use this router when working with:

• Databases (SwiftData, Core Data, GRDB, SQLiteData)
• Schema migrations
• CloudKit sync
• File storage (iCloud Drive, local storage)
• Data serialization (Codable, JSON)
• Storage strategy decisions

Routing Logic

SwiftData

Working with SwiftData → /skill swiftdata Schema migration → /skill swiftdata-migration Migration issues → /skill swiftdata-migration-diag Migrating from Realm → /skill realm-migration-ref SwiftData vs SQLiteData → /skill swiftdata-to-sqlitedata

Other Databases

GRDB queries → /skill grdb SQLiteData → /skill sqlitedata Advanced SQLiteData → /skill sqlitedata-ref Core Data issues → /skill core-data-diag

Migrations

Database migration safety → /skill database-migration (critical - prevents data loss)

Serialization

Codable issues → /skill codable

Cloud Storage

CloudKit → /skill cloudkit-ref iCloud Drive → /skill icloud-drive-ref Cloud sync errors → /skill cloud-sync-diag

File Storage

Storage strategy → /skill storage-strategy Storage issues → /skill storage-diag Storage management → /skill storage-management-ref File protection → /skill file-protection-ref

Decision Tree

User asks about data/storage
  ├─ Database?
  │  ├─ SwiftData? → swiftdata, swiftdata-migration
  │  ├─ Core Data? → core-data-diag
  │  ├─ GRDB? → grdb
  │  └─ SQLiteData? → sqlitedata
  │
  ├─ Migration? → database-migration (ALWAYS - prevents data loss)
  │
  ├─ Cloud storage?
  │  ├─ CloudKit? → cloudkit-ref
  │  ├─ iCloud Drive? → icloud-drive-ref
  │  └─ Sync errors? → cloud-sync-diag
  │
  ├─ Serialization? → codable
  │
  └─ File storage? → storage-strategy, storage-diag, storage-management-ref

Critical Pattern: Migrations

ALWAYS invoke /skill database-migration when adding/modifying database columns.

This prevents:

• "FOREIGN KEY constraint failed" errors
• "no such column" crashes
• Data loss from unsafe migrations

Example Invocations

User: "I need to add a column to my SwiftData model" → Invoke: /skill database-migration (critical - prevents data loss)

User: "How do I query SwiftData with complex filters?" → Invoke: /skill swiftdata

User: "CloudKit sync isn't working" → Invoke: /skill cloud-sync-diag

User: "Should I use SwiftData or SQLiteData?" → Invoke: /skill swiftdata-to-sqlitedata