performance-swiftui-debugging

What problem does it solve?

Diagnoses slow, janky, or excessively re-rendering SwiftUI views and guides developers to targeted fixes that reduce CPU work, preserve state, and restore smooth UI updates. It helps identify why bodies are evaluated too often, when view identity causes recreation, and when eager loading or object allocation in body causes stutters.

Core Features & Use Cases

• Re-evaluation analysis: Guidance on using Self._printChanges() and interpreting body evaluation counts to find which dependencies changed.
• Identity & state fixes: Advice for stable .id() usage, conditional branching patterns, and ForEach identifiers to preserve @State and avoid unnecessary recreation.
• Lazy loading & list performance: Recommendations to replace eager containers with LazyVStack/List and to avoid layout patterns that defeat laziness.
• Practical tools: Walkthroughs for Instruments SwiftUI template, os_signpost measurements, and strategies like extracting subviews, using @Observable, Equatable, and moving work off the main thread.
• Use Case: Improve scroll performance in a large list by replacing VStack+ForEach with LazyVStack, fixing image sizing, and eliminating object creation in body.

Quick Start

Tell the skill which SwiftUI view is slow and paste the view code or describe the observed jank and environment (platform, iOS version, and Xcode Instruments data if available).