swiftui-expert-skill

SwiftUI Expert Skill

Operating Rules

• Consult references/latest-apis.md at the start of every task to avoid deprecated APIs
• Liquid Glass is the system design from the iOS 27 SDK on; design for it by default, and audit an app's UI before moving it to Xcode 27 (use the swiftui-liquid-glass skill)
• Use #available gating with sensible fallbacks for version-specific APIs

SwiftUI Code Workflow

Review existing SwiftUI code

• Read the code under review and identify which topics apply
• Flag deprecated APIs (compare against references/latest-apis.md)
• Run the Topic Router below for each relevant topic
• Validate #available gating and fallback paths for iOS 26+ features

Improve existing SwiftUI code

• Audit current implementation against the Topic Router topics
• Replace deprecated APIs with modern equivalents from references/latest-apis.md
• Refactor hot paths to reduce unnecessary state updates
• Extract complex view bodies into separate subviews
• Suggest image downsampling when UIImage(data:) is encountered (optional optimization, see references/image-optimization.md)

Implement new SwiftUI feature

• Design data flow first: identify owned vs injected state
• Structure views for optimal diffing (extract subviews early)
• Apply correct animation patterns (implicit vs explicit, transitions)
• Use Button for all tappable elements; add accessibility grouping and labels
• Gate version-specific APIs with #available and provide fallbacks

Instruments Trace Workflow

Record a new Instruments trace

Trigger when the user asks to "record a trace", "profile the app", "capture a session", etc. Full reference: references/trace-recording.md.

1. Confirm target — attach to a running app, launch an app, or record all processes? If the user didn't say, ask. List connected devices when useful:

   python3 "${SKILL_DIR}/scripts/record_trace.py" --list-devices
   

2. Pick a template based on target kind — the SwiftUI template populates the SwiftUI lane on any real device: a physical iOS/iPadOS device or the host Mac. The only exception is the iOS Simulator, where the SwiftUI lane comes back empty — switch to --template "Time Profiler" in that case (still gives Time Profiler + Hangs + Animation Hitches). Always check --list-devices: simulators kind → Time Profiler; devices kind (real devices and the host Mac) → default SwiftUI. Full decision table in references/trace-recording.md.
3. Start the recording. For agent-driven sessions where the user says "I'll tell you when I'm done", start in the background and use a stop-file:

   python3 "${SKILL_DIR}/scripts/record_trace.py" \
       --device "<name|udid>" --attach "<AppName>" \
       --stop-file /tmp/stop-trace --output ~/Desktop/session.trace
   

   For interactive sessions, just tell the user to press Ctrl+C when done.
4. Signal stop — when the user says they've finished exercising the app, touch /tmp/stop-trace. The script cleanly SIGINTs xctrace and waits up to 60s for finalisation.
5. Analyse the resulting trace (flow into the "Trace-driven improvement" workflow below).