# IOS Performance

> Profile and optimize iOS apps with Instruments, memory management, and rendering techniques. Use when profiling iOS apps with Instruments or optimizing memory and rendering.

- Skill: `hoangnguyen0403/ios-performance` (Agent Skill, multi-file: 3 files)
- Install (CLI): `npx skillmds add hoangnguyen0403/ios-performance`
- Raw SKILL.md: https://api.skillmd.com/api/skills/hoangnguyen0403/ios-performance/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: HoangNguyen0403 (https://skillmd.com/u/hoangnguyen0403)
- Updated: 2026-08-19
- Page: https://skillmd.com/skills/hoangnguyen0403/ios-performance

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# iOS Performance

## **Priority: P0 (CRITICAL)**

## Implementation Workflow

1. **Profile with Instruments** — Regularly use Allocations and Leaks to detect memory issues. Use Time Profiler for CPU stalls.
2. **Reuse cells** — Always use `dequeueReusableCell` and keep `cellForRowAt` lightweight.
3. **Cache images** — Use `SDWebImage` or `Kingfisher` for remote assets. `AsyncImage` lacks caching for lists.
4. **Offload to background** — Move parsing, encryption, and heavy computation off Main thread using GCD or Tasks.
5. **Enable strict warnings** — Set `SWIFT_TREAT_WARNINGS_AS_ERRORS` in Release builds.
6. **Run static analysis** — Use Xcode's "Analyze" (Product > Analyze) to catch logic errors.

See [background processing and cell reuse examples](references/implementation.md)

## Anti-Patterns

- **No Main-thread Processing**: Offload parsing/processing to background using `Task.detached` or GCD
- **No Manual Cache Clears**: Let system handle low-memory via `applicationDidReceiveMemoryWarning`
- **No Retain Cycles**: Use Leaks instrument frequently during development

## References

- [Profiling & Optimization](references/implementation.md)