swift-optimise

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Swift 6.2 and SwiftUI performance optimization for iOS 26 clinic architecture codebases. Covers async/await concurrency patterns, Sendable/actor isolation, view/render performance, and animation performance while preserving modular MVVM-C boundaries across App, Feature, Domain, and Data layers. Use when profiling or optimizing Swift/SwiftUI behavior in clinic modules.

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Sourcepproenca/dot-skills

Added on2026-02-22

NPX Install

npx skill4agent add pproenca/dot-skills swift-optimise

SKILL.md Content

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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