ios-performance

name	ios-performance
description	Standards for Instruments, Memory Management, and Optimization. Use when profiling iOS apps with Instruments or optimizing memory and rendering. (triggers: **/*.swift, Instruments, Allocations, Leaks, dequeueReusableCell)

iOS Performance Standards

Priority: P0

Implementation Guidelines

Diagnostic Tools

• Instruments: Regularly use Allocations and Leaks to detect memory issues.
• Time Profiler: Identify heavy CPU tasks and Main Thread stalls.
• Network instrument: Analyze request payload sizes and frequency.

Optimization

• Table/Collection Views: Always use dequeueReusableCell and keep cellForRowAt logic lightweight.
• Image Caching: Use SDWebImage or Kingfisher for remote assets to prevent redundant fetching and main-thread decoding. (Note: AsyncImage lacks built-in caching; prioritize third-party for lists).
• Background threads: Offload expensive work (parsing, encryption) from the Main thread using GCD or Tasks.

Diagnostics

• Compiler Warnings: Enable SWIFT_TREAT_WARNINGS_AS_ERRORS in Release builds.
• Static Analyzer: Use Xcode's "Analyze" (Product > Analyze) to find logic errors.

Anti-Patterns

• No parsing/processing on Main: Use background thread.
• No redundant cache clears: Let system handle low-memory via AppDelegate.
• No undetected retain cycles: Use Leaks instrument frequently.

References

• Profiling & Optimization