Swift 6 Concurrency Guide

Purpose: Progressive journey from single-threaded to concurrent Swift code Swift Version: Swift 6.0+, Swift 6.2+ for @concurrent iOS Version: iOS 17+ (iOS 18.2+ for @concurrent) Xcode: Xcode 16+ (Xcode 16.2+ for @concurrent) Context: WWDC 2025-268 "Embracing Swift concurrency" - approachable path to data-race safety

When to Use This Skill

✅ Use this skill when:

• Starting a new project and deciding concurrency strategy
• Debugging Swift 6 concurrency errors (actor isolation, data races, Sendable warnings)
• Deciding when to introduce async/await vs concurrency
• Implementing @MainActor classes or async functions
• Converting delegate callbacks to async-safe patterns
• Deciding between @MainActor, nonisolated, @concurrent, or actor isolation
• Resolving "Sending 'self' risks causing data races" errors
• Making types conform to Sendable