Guide SwiftUI development for macOS apps. Whether writing new code or reviewing existing code, apply deep understanding of SwiftUI's runtime behavior — how the observation registrar dispatches, how the attribute graph diffs view trees, how actor isolation interacts with view lifecycles.
How to Use
Writing code: Load relevant references before implementation. The patterns here prevent bugs that are expensive to find later — observation cascades, identity thrashing, concurrency overhead. When making architecture decisions (state ownership, view decomposition, AppKit bridging), consult the relevant reference for tradeoffs.
Reviewing code: Check each reference area systematically. Focus on genuine problems — observation inefficiencies, deprecated API, accessibility gaps, concurrency anti-patterns. Don't flag obvious issues or invent problems.
Partial scope: Load only what the task needs. Not every change requires all eight references.
References
| Reference | Load when |
|---|---|
references/observation.md | @Observable, @State, ForEach, data-driven views, Observations {} streams |
references/concurrency.md | Task, async/await, actors, DispatchQueue, AsyncStream, scheduling decisions |
references/performance.md | View composition, animations, gestures, large collections, Canvas, TimelineView |
references/views.md | View decomposition, navigation, .task(id:), preference keys, custom Layout |
references/data.md | State architecture, SwiftData, environment injection, bindings, persistence |
references/platform.md | NSViewRepresentable, NSHostingView, multi-window, AppKit bridging, window chrome |
references/api.md | API choice, deprecated patterns, modern Swift/SwiftUI idioms |
references/accessibility.md | VoiceOver, keyboard navigation, Dynamic Type, Reduce Motion |
Principles
- Target macOS 26+, Swift 6.2 with strict concurrency and
@MainActordefault isolation. - Check whether the project enables
NonisolatedNonsendingByDefault(SE-0461) — this changes wherenonisolatedasync functions execute. Seereferences/concurrency.md. - Prefer SwiftUI-native solutions. Use AppKit (
NSViewRepresentable,NSHostingView,NSWindow) only when SwiftUI has no equivalent. - Understand the mechanism. When suggesting a pattern, know why it works — what the observation registrar does, what the attribute graph diffing costs, what
_modifyvssetmeans for notification. Rules without understanding produce cargo-culted code. - Do not introduce third-party frameworks without asking. Apple's open-source Swift packages (
swift-collections,swift-algorithms,swift-async-algorithms) are exceptions — prefer them over reimplementing non-trivial data structures or algorithms. Seereferences/api.md.
Examples
User: "Review observation patterns in these sidebar views"
→ Load references/observation.md. Check each file for: state capture in ForEach, non-Equatable types on observed properties, missing @ObservationIgnored on caches, _modify vs set notification waste.
User: "I need to embed an NSCollectionView in SwiftUI"
→ Load references/platform.md. Apply NSViewRepresentable lifecycle, Equatable conformance for update gating, Coordinator for delegates.
User: "This view is re-rendering too much, help me debug it"
→ Load references/performance.md and references/observation.md. Check view identity (structural vs explicit), observation scope (are unrelated properties tracked in the same body?), @State vs @Observable for gesture-driven values.
Review Output
Organize findings by file. For each issue:
- File and relevant line(s).
- The pattern being violated and why it matters at the runtime level.
- Brief before/after code fix.
Skip clean files. End with a prioritized summary of the most impactful changes.