// Use when building features with TCA (The Composable Architecture), structuring reducers, managing state, handling effects, navigation, or testing TCA features. Covers @Reducer, Store, Effect, TestStore, reducer composition, and TCA patterns.
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.
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.
Use when writing async/await code, enabling strict concurrency, fixing Sendable errors, migrating from completion handlers, managing shared state with actors, or using Task/TaskGroup for concurrency.
Use when implementing on-device AI with Apple's Foundation Models framework (iOS 26+), building summarization/extraction/classification features, or using @Generable for type-safe structured output.
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.
Use when adding haptic feedback for user confirmations (button presses, toggles, purchases), error notifications, or custom tactile patterns (Core Haptics). Covers UIFeedbackGenerator and CHHapticEngine patterns.
| name | composable-architecture |
| description | Use when building features with TCA (The Composable Architecture), structuring reducers, managing state, handling effects, navigation, or testing TCA features. Covers @Reducer, Store, Effect, TestStore, reducer composition, and TCA patterns. |
TCA provides architecture for building complex, testable features through composable reducers, centralized state management, and side effect handling. The core principle: predictable state evolution with clear dependencies and testable effects.
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 |
|---|---|
| Reducer Structure | Creating new reducers, setting up @Reducer, State, Action, or @ViewAction |
| Views - Binding | Using @Bindable, two-way bindings, store.send(), or .onAppear/.task |
| Views - Composition | Using ForEach with stores, scoping to child features, or optional children |
| Navigation - Basics | Setting up NavigationStack, path reducers, pushing/popping, or programmatic dismiss |
| Navigation - Advanced | Deep linking, recursive navigation, or combining NavigationStack with sheets |
| Shared State | Using @Shared, .appStorage, .withLock, or sharing state between features |
| Dependencies | Creating @DependencyClient, using @Dependency, or setting up test dependencies |
| Effects | Using .run, .send, .merge, timers, effect cancellation, or async work |
| Presentation | Using @Presents, AlertState, sheets, popovers, or the Destination pattern |
| Testing - Fundamentals | Setting up test suites, makeStore helpers, or understanding Equatable requirements |
| Testing - Patterns | Testing actions, state changes, dependencies, errors, or presentations |
| Testing - Advanced | Using TestClock, keypath matching, exhaustivity = .off, or time-based tests |
| Testing - Utilities | Test data factories, LockIsolated, ConfirmationDialogState testing, or @Shared testing |
| Performance | Optimizing state updates, high-frequency actions, memory, or store scoping |
Over-modularizing features — Breaking features into too many small reducers makes state management harder and adds composition overhead. Keep related state and actions together unless there's genuine reuse.
Mismanaging effect lifetimes — Forgetting to cancel effects when state changes leads to stale data, duplicate requests, or race conditions. Use .concatenate for sequential effects and .cancel when appropriate.
Navigation state in wrong places — Putting navigation state in child reducers instead of parent causes unnecessary view reloads and state inconsistencies. Navigation state belongs in the feature that owns the navigation structure.
Testing without TestStore exhaustivity — Skipping TestStore assertions for "simple" effects or "obvious" state changes means you miss bugs. Use exhaustivity checking religiously; it catches regressions early.
Mixing async/await with Effects incorrectly — Converting async/await to .run effects without proper cancellation or error handling loses isolation guarantees. Wrap async operations carefully in .run with yield statements.