IOS Performance Debugging

iOS Performance Debugging

Workflow

1. Define one reproducible user flow and one metric before changing code.
2. Capture device, OS, build configuration, commit, data fixture, and baseline trace.
3. Use the narrowest instrument: SwiftUI updates and hitches, Time Profiler, Allocations/Leaks, Network, Energy, or concurrency analysis.
4. Correlate the trace to source. Do not optimize from intuition alone.
5. Change one ownership, identity, layout, allocation, or scheduling cause at a time.
6. Repeat the same flow and compare the same metric.
7. Keep the trace, command, and before-after result in the handoff.

SwiftUI checks

• Stable identity in collections.
• Observation scoped to data the view actually reads.
• No expensive formatting, filtering, I/O, or object creation in body.
• Lazy containers used only where they fit the layout.
• Image decoding and resizing moved off the render-critical path.
• Navigation and sheet state represented by one source of truth.

Read references/trace-receipt.md before claiming a performance improvement.