Concurrency & Async

Master Swift's concurrency model and catch data races at compile time with strict concurrency patterns.

Skills

• Swift Concurrency – Swift 6 strict concurrency patterns, async/await, MainActor, Sendable, and actor isolation

  • "I'm getting 'Main actor-isolated property accessed from nonisolated context' errors everywhere."
  • "My code is throwing 'Type does not conform to Sendable' warnings when passing data between threads."
  • "I have a stored task causing memory leaks. How do I write it correctly with weak self?"

• assumeIsolated – Synchronous actor access for tests, legacy callbacks, and performance-critical code

  • "How do I access MainActor state from a delegate callback that runs on main thread?"
  • "What's the difference between Task { @MainActor in } and MainActor.assumeIsolated?"

• Synchronization – Thread-safe primitives: Mutex (iOS 18+), OSAllocatedUnfairLock, Atomic types

  • "Should I use Mutex or actor for this hot path?"
  • "What's the difference between os_unfair_lock and OSAllocatedUnfairLock?"

• Ownership Conventions – borrowing/consuming modifiers for performance and noncopyable types

  • "What does borrowing do in Swift?"
  • "How do I use ~Copyable types?"

• Concurrency Profiling – Instruments workflows for async/await performance

  • "My async code is slow, how do I profile it?"
  • "I think I have actor contention, how do I diagnose it?"