What's the best way to use async in Swift

The best way to use async in Swift involves leveraging the async and await keywords to handle asynchronous operations. Here are the key points:

Task Suspension: When a task is waiting for an asynchronous operation to complete, it suspends to yield the CPU to other tasks. This is modeled in code using the async and await syntax. A function that may suspend is marked with the async keyword, and when calling an async function, the await keyword is used to indicate that a suspension can occur on that line. This allows other tasks to run while waiting for the async operation to complete.
Concurrency Features: Swift's concurrency features include tasks, async/await, and actors. Tasks represent independent concurrent execution contexts and are lightweight, allowing for the creation of many tasks. Tasks can execute concurrently, making them suitable for handling operations like HTTP requests.
Actors: Actors are reference types that encapsulate shared mutable state and automatically protect their state by serializing accesses. Calls to actor methods from outside the context of the actor are asynchronous, ensuring safe concurrent access.
Testing with Async: When writing concurrent test code, you can use the same concurrency features in Swift as in production code. The await keyword works the same way in tests, allowing other test code to keep the CPU busy while work is pending. For older code using completion handlers, Swift provides async overloads or you can use withCheckedContinuation to convert it to an awaitable expression.

For more detailed information, you can refer to the following sessions from WWDC 2024:

These sessions cover the basics of writing concurrent code in Swift, the use of actors, and techniques for testing asynchronous conditions.