swift-optimise

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 26 / Swift 6.2 with @Observable and Swift 6 strict concurrency. Clinic Architecture Contract (iOS 26 / Swift 6.2) All guidance in this skill assumes the clinic modular MVVM-C architecture: Feature modules import Domain + DesignSystem only (never Data , never sibling features) App target is the convergence point and owns DependencyContainer , concrete coordinators, and Route Shell wiring Domain stays pure Swift and defines models plus repository, *Coordinating , ErrorRouting , and AppError contracts Data owns SwiftData/network/sync/retry/background I/O and implements Domain protocols Read/write flow defaults to stale-while-revalidate reads and optimistic queued writes ViewModels call repository protocols directly (no default use-case/interactor layer) 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 Priority Category Impact Prefix 1 Concurrency & Async CRITICAL conc- 2 Render & Scroll Performance HIGH perf- 3 Animation Performance MEDIUM anim- 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 File Description references/_sections.md Category definitions and ordering assets/templates/_template.md Template for new rules