Explain concurrency contexts

Concurrency contexts in Swift refer to the way tasks are managed and executed across different threads or queues in an application. In the context of migrating an app to Swift 6, concurrency is handled more explicitly and safely, thanks to Swift's concurrency model.

In the original app setup, concurrency was managed using multiple concurrent queues, including the main queue for UI and model work, a dispatch queue for background tasks, and arbitrary queues for certain callbacks. This setup could lead to confusion and potential data races, as it wasn't always clear which queue was executing code at any given time.

With Swift concurrency, the architecture becomes more organized. The main actor is used for UI views and models, ensuring that these components run on the main thread. Background operations are performed on dedicated actors, which helps in managing concurrency more predictably and safely.

Swift 6 introduces data race safety by default, turning potential data race issues into compile-time errors. This is achieved through mechanisms like actors for protecting mutable state and the Sendable protocol for safe data sharing. By enabling strict concurrency checking, developers can identify and resolve concurrency issues during development, reducing runtime errors and improving app stability.

For more detailed information on concurrency contexts and how to migrate your app to Swift 6, you can refer to the session Migrate your app to Swift 6 (08:53).