Fix 'main actor-isolated property can not be referenced from a nonisolated context' in Swift 6 with four compiled fixes and a snapshot pattern.

RocketLaunch (Next Rocket Launch) is a free SwiftUI teaching app with feature actors, three providers, deliberate failure handling and a GCD comparison project.

Enable complete concurrency checking in Xcode or Package.swift, switch targets to Swift 6 mode, and optionally use default MainActor isolation. Tested.

No deadline for Swift 6 language mode, but since 28 April 2026 App Store uploads need Xcode 26 (Swift 6.2). Here's what's required and what's optional.

Big bang, file by file or feature slices? A behaviour-first, slice-by-slice Swift 6 migration strategy with leaf modules first and tested CFA examples.

Xcode 26's Swift 6.2 compiler still builds Swift 5 mode. Learn what Swift 6 mode changes, which upcoming features it enables, and how to switch per target.

Migrate to Swift 6 feature by feature: record behaviour, enable complete checking, wrap callbacks, move state to owners, then switch targets. Tested code.

Swift 6 turns Sendable violations into errors but allows safe hand-overs with region-based isolation and sending. See what changed, compiled in each mode.

Swift 6 enforces @MainActor isolation, requires owners for static state, drops wrapper inference, and Swift 6.2 adds default MainActor and isolated deinit.

MainActor.run hops to the main actor and back. Learn when it fits, why @MainActor ViewModels don't need it, and how to migrate DispatchQueue.main.async.

Swift 6.4 lets you await in defer (SE-0493) and shield cleanup from cancellation with withTaskCancellationShield (SE-0504). When and how to make cleanup finish.

Swift 6.2's @concurrent explained: why nonisolated async functions now run on the caller's actor, when to use @concurrent, and how to migrate safely.

Task.checkCancellation vs Task.isCancelled in Swift: when to throw CancellationError, when to return quietly, where to put the checks, and which tasks inherit cancellation.

How withTaskCancellationHandler works in Swift: when onCancel runs, why it can't touch actor state, and safe patterns for continuations and callbacks.

Turn repeating callbacks into a for await loop with AsyncStream. Learn yield, finish, onTermination, buffering and a real Swift 6 actor example.

Wrap a completion handler in withCheckedContinuation and resume exactly once. Learn throwing, delegate and cancellable continuations with Swift 6 code.

How a real GCD metronome app was migrated to CFA and Swift Concurrency: audio off the main actor, Combine to Observation, and an honest regression.