Agent skill
grdb
Use when writing raw SQL with GRDB, complex joins across 4+ tables, window functions, ValueObservation for reactive queries, or dropping down from SQLiteData for performance. Direct SQLite access for iOS/macOS with type-safe queries and migrations.
Install this agent skill to your Project
npx add-skill https://github.com/johnrogers/claude-swift-engineering/tree/main/plugins/swift-engineering/skills/grdb
SKILL.md
GRDB
Direct SQLite access using GRDB.swift - type-safe Swift wrapper with full SQLite power when you need it.
Reference Loading Guide
ALWAYS load reference files if there is even a small chance the content may be required. It's better to have the context than to miss a pattern or make a mistake.
| Reference | Load When |
|---|---|
| Getting Started | Setting up DatabaseQueue or DatabasePool |
| Queries | Writing raw SQL, Record types, type-safe queries |
| Value Observation | Reactive queries, SwiftUI integration |
| Migrations | DatabaseMigrator, schema evolution |
| Performance | EXPLAIN QUERY PLAN, indexing, profiling |
When to Use GRDB vs SQLiteData
| Scenario | Use |
|---|---|
| Type-safe @Table models | SQLiteData |
| CloudKit sync needed | SQLiteData |
| Complex joins (4+ tables) | GRDB |
| Window functions (ROW_NUMBER, RANK) | GRDB |
| Performance-critical raw SQL | GRDB |
| Reactive queries (ValueObservation) | GRDB |
Core Workflow
- Choose DatabaseQueue (single connection) or DatabasePool (concurrent reads)
- Define migrations with DatabaseMigrator
- Create Record types (Codable, FetchableRecord, PersistableRecord)
- Write queries with raw SQL or QueryInterface
- Use ValueObservation for reactive updates
Requirements
- iOS 13+, macOS 10.15+
- Swift 5.7+
- GRDB.swift 6.0+
Common Mistakes
-
Performance assumptions without EXPLAIN PLAN — Assuming your query is fast or slow without checking
EXPLAIN QUERY PLANis guessing. Always profile queries with EXPLAIN before optimizing. -
Missing indexes on WHERE clauses — Queries filtering on non-indexed columns scan the entire table. Index any column used in WHERE, JOIN, or ORDER BY clauses for large tables.
-
Improper migration ordering — Running migrations out of order or skipping intermediate versions breaks schema consistency. Always apply migrations sequentially; never jump versions.
-
Record conformance shortcuts — Not conforming Record types to
PersistableRecordorFetchableRecordcorrectly leads to silent data loss or deserialization failures. Always implement all required protocols correctly. -
ValueObservation without proper cleanup — Forgetting to cancel ValueObservation when views disappear causes memory leaks and stale data subscriptions. Store the cancellable and clean up in deinit.
Recommended Agent Skills
Expand your agent's capabilities with these related and highly-rated skills.
swiftui-advanced
Use when implementing gesture composition (simultaneous, sequenced, exclusive), adaptive layouts (ViewThatFits, AnyLayout, size classes), or choosing architecture patterns (MVVM vs TCA vs vanilla, State-as-Bridge). Covers advanced SwiftUI patterns beyond basic views.
ios-hig
Use when designing iOS interfaces, implementing accessibility (VoiceOver, Dynamic Type), handling dark mode, ensuring adequate touch targets, providing animation/haptic feedback, or requesting user permissions. Apple Human Interface Guidelines for iOS compliance.
ios-26-platform
Use when implementing iOS 26 features (Liquid Glass, new SwiftUI APIs, WebView, Chart3D), deploying iOS 26+ apps, or supporting backward compatibility with iOS 17/18.
swiftui-patterns
Use when implementing iOS 17+ SwiftUI patterns: @Observable/@Bindable, MVVM architecture, NavigationStack, lazy loading, UIKit interop, accessibility (VoiceOver/Dynamic Type), async operations (.task/.refreshable), or migrating from ObservableObject/@StateObject.
swift-testing
Use when writing tests with Swift Testing (@Test,
localization
Use when implementing internationalization (i18n), String Catalogs, pluralization, or right-to-left layout support. Covers modern localization workflows with Xcode String Catalogs and LocalizedStringKey patterns.
Didn't find tool you were looking for?