Swiftui Dev

SwiftUI Dev

Use this skill for SwiftUI development, architecture, structure, performance, and Apple native app profiling. It combines:

• SwiftUI view refactor and Observation/MV guidance.
• SwiftUI code-first performance audit.
• Native macOS/iOS Time Profiler CLI workflow with xctrace, atos, and included scripts.

Do not use this skill for web performance, server profiling, generic PR review, product planning, or non-Apple UI frameworks. For ordinary implementation work without SwiftUI architecture/performance/native profiling concerns, use the development skill.

Route The Work

If the user provides only symptoms, start with code-first SwiftUI review. Ask for trace/screenshots only when code review is inconclusive or the user explicitly wants trace analysis.

Required Inputs

For SwiftUI code review:

• Target view or feature code.
• Data flow: @State, @Binding, @Environment, @Observable, @Query, services, models.
• Symptoms and reproduction steps.
• Device/OS/build configuration when performance is involved.

For native profiling:

• App name and binary path, or existing .trace bundle.
• Attach PID or launch binary path.
• Slow interaction to exercise during capture.
• Capture duration, defaulting to 90 seconds.
• Matching symbols / binary and permission to launch or attach.

Proceed with explicit assumptions for code-only reviews. Stop before profiling if required tools or permissions are missing.

Core Workflow

1. Classify the task: SwiftUI structure/refactor, SwiftUI performance, or native trace profiling.
2. Start code-first for SwiftUI: inspect structure, data flow, Observation ownership, identity, layout, and body work before requesting heavier tooling.
3. Use Instruments evidence when available: treat traces/screenshots/CSV as evidence, not as the whole answer.
4. Make targeted recommendations: order issues by likely impact and confidence.
5. Verify with the same scenario: compare before/after CPU, frame drops, memory peak, sample counts, or the specific user-visible symptom when data exists.

Boundaries

• Do not invent metrics, trace findings, sample counts, call stacks, device settings, or benchmark results.
• Do not run xctrace unless the user has provided a local target, trace, or explicit permission and the environment is macOS with Xcode tools.
• Do not interpret stale symbols as real hotspots. Binary, trace, and load address must match.
• Do not introduce ViewModels by default. Prefer SwiftUI-native state/data flow unless existing code or user requirements justify a view model.
• Do not change business logic during refactor unless the user explicitly asks.
• If source files must be edited, follow the existing project style and verify with relevant build/tests/profiling.

Output Format

Use this concise structure unless a reference template is more specific:

# SwiftUI Dev Review: [Target]

## Inputs And Assumptions

## Findings
| Priority | Finding | Evidence | Recommendation | Confidence |
|---|---|---|---|---|

## Suggested Changes

## Verification Plan

## Risks / Limits

## Handoff To Next Stage

For native trace analysis, use the report structure in references/native-trace.md.

Quality Checklist

Before finalizing, verify:

• The task is Apple-native or SwiftUI-specific.
• SwiftUI structure recommendations preserve clear data ownership and framework-native state flow.
• Findings cite code, trace evidence, screenshots, or clearly labeled assumptions.
• Recommendations are targeted, not generic "optimize everything" advice.
• Refactors preserve behavior unless requested otherwise.
• Profiling commands, trace path, binary path, load address, and confidence are reported when CLI profiling is used.
• The user gets a concrete verification plan.