---

name: ios-performance description: Profile and optimize iOS apps with Instruments, memory management, and rendering techniques. Use when profiling iOS apps with Instruments or optimizing memory and rendering. metadata: triggers: files: - '**/*.swift' keywords: - Instruments - Allocations - Leaks - dequeueReusableCell - ios performance - swift performance - optimize ios - time profiler - frame drops - main thread - slow scroll

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

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