swift-best-practices

Async/await in Swift 6 replaces callbacks with structured concurrency. Use `async` functions for asynchronous work and `MainActor` to ensure UI updates run on the main thread. Combine with `Sendable` types to prevent data races and guarantee thread safety across concurrent tasks.

Swift 6 enforces strict data-race safety by default, requiring `Sendable` conformance and actor isolation. Migration involves updating completion handlers to async/await, protecting mutable state with actors, and marking thread-safe types as `Sendable` to meet the compiler's safety requirements.

Swift API design requires clear naming conventions, comprehensive documentation for public declarations, and fluent parameter guidelines. Follow Swift naming standards for methods and properties, document thread safety and parameter requirements, and ensure your API is intuitive and maintainable for other developers.

This Skill applies to iOS and macOS projects targeting macOS 15.7 and later. Swift 6 concurrency features require modern deployment targets; if your project targets older versions, you'll need to maintain Swift 5 patterns or gradually increase your minimum deployment target.

Common pitfalls include forgetting to mark shared mutable state with actors, missing `Sendable` conformance on types passed between tasks, and unsafe access to main-thread resources outside `MainActor`. This Skill guides you through these patterns to prevent data races and maintain thread safety.

You can incrementally migrate to async/await; mixing patterns is supported. Start with new code and high-priority modules, then gradually convert existing completion handler-based code. This Skill provides strategies to manage the transition without rewriting everything at once.