Tell me basics of concurrency

Concurrency in Swift is a powerful feature that allows you to perform multiple tasks simultaneously, improving the efficiency and responsiveness of your applications. Here are some basics of concurrency in Swift:

1. Data Race Safety: One of the primary goals of Swift concurrency is to ensure data race safety. Data races occur when multiple threads access shared data simultaneously, and at least one thread modifies the data. This can lead to unpredictable behavior and crashes. Swift 6 achieves data race safety by default, turning potential data race issues into compile-time errors, which significantly improves the security and stability of your app (What’s new in Swift).

2. Concurrency Architecture: In Swift, concurrency can be managed using actors and the async/await pattern. Actors are used to protect mutable state and ensure that only one task can access the state at a time. The async/await pattern allows you to write asynchronous code that is easy to read and maintain. For example, UI views and models can run on the main actor, while background operations are performed on dedicated actors (Migrate your app to Swift 6).

3. Structured Concurrency: Swift's structured concurrency model helps organize concurrent code in a clear and manageable way. Tasks are used to represent units of work that can be executed concurrently. The await keyword is used to pause the execution of a task until the awaited task completes. This model helps avoid the hidden complexity of concurrency and makes the code easier to understand and maintain (A Swift Tour: Explore Swift’s features and design).

4. Adopting Concurrency Features: When migrating to Swift 6, you can gradually adopt concurrency features. For instance, you can enable strict concurrency checking in your project's build settings to identify and fix potential concurrency issues. This can be done on a per-target basis, allowing you to incrementally update your codebase (Migrate your app to Swift 6).

5. Handling Legacy Code: When working with legacy code or third-party libraries that are not yet updated for Swift concurrency, you may encounter challenges. Swift provides mechanisms to handle these situations, such as using the @preconcurrency attribute to indicate that certain code is not concurrency-safe (Migrate your app to Swift 6).

For a more detailed exploration of concurrency in Swift, you can refer to the session A Swift Tour: Explore Swift’s features and design which covers concurrency starting at 18:33.