Apple Swift/SwiftUI Performance Optimization Best Practices

Comprehensive guide for Swift and SwiftUI performance optimization. Contains 19 rules across 3 categories covering modern concurrency, render performance, and animation performance. Targets iOS 17+ with @Observable and Swift 6 strict concurrency.

When to Apply

Reference these guidelines when:

• Migrating to Swift 6 strict concurrency (Sendable, actor isolation)
• Replacing Combine publishers with async/await
• Implementing @MainActor isolation and actor-based concurrency
• Decomposing views to reduce state invalidation blast radius
• Optimizing scroll and render performance with lazy containers
• Using Canvas/TimelineView for high-performance rendering
• Profiling with SwiftUI Instruments before optimizing
• Building performant spring animations and transitions

Rule Categories by Priority

Quick Reference

1. Concurrency & Async (CRITICAL)

• conc-combine-to-async – Replace Combine publishers with async/await
• conc-mainactor-isolation – Use @MainActor instead of DispatchQueue.main
• conc-swift6-sendable – Adopt Sendable and Swift 6 strict concurrency
• conc-task-id-pattern – Use .task(id:) for reactive data loading
• conc-actor-for-shared-state – Replace lock-based shared state with actors
• conc-asyncsequence-streams – Replace NotificationCenter observers with AsyncSequence

2. Render & Scroll Performance (HIGH)

• perf-view-decomposition – Decompose views to limit state invalidation blast radius
• perf-instruments-profiling – Profile with SwiftUI Instruments before optimizing
• perf-lazy-containers – Use lazy containers for large collections
• perf-canvas-timeline – Use Canvas and TimelineView for high-performance rendering
• perf-drawinggroup – Use drawingGroup for complex graphics
• perf-equatable-views – Add Equatable conformance to prevent spurious redraws
• perf-task-modifier – Use .task modifier instead of .onAppear for async work
• perf-async-image – Use AsyncImage with caching strategy for remote images

3. Animation Performance (MEDIUM)

• anim-spring – Use spring animations as default
• anim-matchedgeometry – Use matchedGeometryEffect for shared transitions
• anim-gesture-driven – Make animations gesture-driven
• anim-with-animation – Use withAnimation for state-driven transitions
• anim-transition-effects – Apply transition effects for view insertion and removal

How to Use

Read individual reference files for detailed explanations and code examples:

• Section definitions – Category structure and impact levels
• Rule template – Template for adding new rules

Reference Files