以下为本文档的中文说明

该技能用于审计SwiftUI应用的性能问题，通过代码审查和性能分析证据来发现和诊断性能瓶颈。SwiftUI是Apple的声明式UI框架，其性能问题可能源于视图过度重建、不必要的状态更新、大型列表渲染优化不足或动画性能不佳等。该技能提供系统化的审计流程，帮助开发者识别和分析SwiftUI应用中的性能问题，并提供针对性的优化建议。适用于iOS和macOS应用开发者需要确保应用界面流畅度和响应性的场景，特别是在处理复杂UI布局和大数据量展示时。该技能提供了详细的操作指南和最佳实践，帮助用户快速上手并深入掌握。通过系统的功能模块划分和丰富的应用场景说明，用户可以在实际项目中有效运用该技能提升工作效率。该技能注重实用性和可操作性，涵盖从基础配置到高级功能的完整知识体系，满足不同层次用户的学习需求。持续更新和优化的内容确保用户始终能够接触到最新的技术发展和行业实践。通过此技能的学习和应用，用户可以减少摸索时间，快速获得可用的解决方案，将精力集中在核心业务逻辑和创新工作上，从而在技术快速迭代的环境中保持竞争力。该技能的模块化设计使其易于扩展和定制，用户可以根据自身需求灵活调整应用方式，实现最大化的价值产出。该技能整合了常见的设计模式和最佳实践，提供了清晰的学习路径和参考资料，帮助用户在短时间内建立起完整的知识框架，并有能力在实际项目中灵活运用所学内容解决问题。

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SwiftUI Performance Audit

Quick start

Use this skill to diagnose SwiftUI performance issues from code first, then request profiling evidence when code review alone cannot explain the symptoms.

When to Use

• When the user reports slow rendering, janky scrolling, layout thrash, or high CPU in SwiftUI.
• When you need a code-first audit plus Instruments guidance if profiling evidence is required.

Workflow

1. Classify the symptom: slow rendering, janky scrolling, high CPU, memory growth, hangs, or excessive view updates.
2. If code is available, start with a code-first review using references/code-smells.md.
3. If code is not available, ask for the smallest useful slice: target view, data flow, reproduction steps, and deployment target.
4. If code review is inconclusive or runtime evidence is required, guide the user through profiling with references/profiling-intake.md.
5. Summarize likely causes, evidence, remediation, and validation steps using references/report-template.md.

1. Intake

Collect:

• Target view or feature code.
• Symptoms and exact reproduction steps.
• Data flow: @State, @Binding, environment dependencies, and observable models.
• Whether the issue shows up on device or simulator, and whether it was observed in Debug or Release.

Ask the user to classify the issue if possible:

• CPU spike or battery drain
• Janky scrolling or dropped frames
• High memory or image pressure
• Hangs or unresponsive interactions
• Excessive or unexpectedly broad view updates

For the full profiling intake checklist, read references/profiling-intake.md.

2. Code-First Review

Focus on:

• Invalidation storms from broad observation or environment reads.
• Unstable identity in lists and ForEach.
• Heavy derived work in body or view builders.
• Layout thrash from complex hierarchies, GeometryReader, or preference chains.
• Large image decode or resize work on the main thread.
• Animation or transition work applied too broadly.

Use references/code-smells.md for the detailed smell catalog and fix guidance.

Provide:

• Likely root causes with code references.
• Suggested fixes and refactors.
• If needed, a minimal repro or instrumentation suggestion.

3. Guide the User to Profile

If code review does not explain the issue, ask for runtime evidence:

• A trace export or screenshots of the SwiftUI timeline and Time Profiler call tree.
• Device/OS/build configuration.
• The exact interaction being profiled.
• Before/after metrics if the user is comparing a change.

Use references/profiling-intake.md for the exact checklist and collection steps.

4. Analyze and Diagnose

• Map the evidence to the most likely category: invalidation, identity churn, layout thrash, main-thread work, image cost, or animation cost.
• Prioritize problems by impact, not by how easy they are to explain.
• Distinguish code-level suspicion from trace-backed evidence.
• Call out when profiling is still insufficient and what additional evidence would reduce uncertainty.

5. Remediate

Apply targeted fixes:

• Narrow state scope and reduce broad observation fan-out.
• Stabilize identities for ForEach and lists.
• Move heavy work out of body into derived state updated from inputs, model-layer precomputation, memoized helpers, or background preprocessing. Use @State only for view-owned state, not as an ad hoc cache for arbitrary computation.
• Use equatable() only when equality is cheaper than recomputing the subtree and the inputs are truly value-semantic.
• Downsample images before rendering.
• Reduce layout complexity or use fixed sizing where possible.

Use references/code-smells.md for examples, Observation-specific fan-out guidance, and remediation patterns.

6. Verify

Ask the user to re-run the same capture and compare with baseline metrics.
Summarize the delta (CPU, frame drops, memory peak) if provided.

Outputs

Provide:

• A short metrics table (before/after if available).
• Top issues (ordered by impact).
• Proposed fixes with estimated effort.

Use references/report-template.md when form
atting the final audit.

References

• Profiling intake and collection checklist: references/profiling-intake.md
• Common code smells and remediation patterns: references/code-smells.md
• Audit output template: references/report-template.md
• Add Apple documentation and WWDC resources under references/ as they are supplied by the user.
• Optimizing SwiftUI performance with Instruments: references/optimizing-swiftui-performance-instruments.md
• Understanding and improving SwiftUI performance: references/understanding-improving-swiftui-performance.md
• Understanding hangs in your app: references/understanding-hangs-in-your-app.md
• Demystify SwiftUI performance (WWDC23): references/demystify-swiftui-performance-wwdc23.md

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.