Instrumentsでプロファイリングする

Guessing where an app is slow wastes time. Instruments is Apple's profiler that shows you exactly what is costing frames.

Choose Product, Profile in Xcode. It builds a release-style binary and launches Instruments attached to your running app.

Instruments offers templates like Time Profiler, Animation Hitches, and SwiftUI. Each focuses on a different kind of slowdown.

The SwiftUI instrument records how often each view's body runs and how long updates take, perfect for redraw hunting.

Look for views with a surprisingly high body count. Those are recomputing too often and are prime targets to scope down.

The Animation Hitches tool flags frames that arrive late. Each hitch is a visible stutter your users actually feel.

The Time Profiler samples the call stack to show which functions burn the most CPU during a slow interaction.

UI must stay on the main thread. If profiling shows heavy work there, move it to a background task to free up frames.

Always measure a release build. Debug builds add checks that distort timings and can hide the real performance picture.

The simulator uses your Mac's power. Profile on an actual device, ideally an older one, to see true user performance.

Profiling is a loop: find a hot spot, make one fix, then re-measure to confirm it helped before moving on.

Which build should you profile for accurate performance numbers?

You learned to profile with Instruments, find frequent body calls and hitches, and re-measure each fix on a real device. 🔍