How do I use async functions?

To use async functions in Swift, you need to understand a few key concepts and syntax. Here are the main points:

1. Marking Functions as Async: A function that may suspend is marked with the async keyword. This indicates that the function can perform asynchronous operations.

2. Using Await: When calling an async function, you use the await keyword to indicate that a suspension can occur at that line. This allows the function to yield control back to the system while waiting for the asynchronous operation to complete.

3. Task Suspension: When an async function is waiting for an operation to complete, it suspends to yield the CPU to other tasks. This is modeled in code using the async and await keywords.

4. Memory Allocation: Async functions allocate their local state on a separate stack from the C stack. They are split into multiple functions at runtime, with each partial function handling a segment of the async function's execution.

5. Partial Functions: An async function is split into partial functions that span the gaps between potential suspension points. Each partial function runs like an ordinary C function until the next suspension point.

Here are some relevant segments from WWDC sessions that explain these concepts in more detail:

• Explore Swift performance:

  • Async functions (24:33)
  • Partial functions (26:46)

• A Swift Tour: Explore Swift’s features and design:

  • Concurrency (18:33)

• Go further with Swift Testing:

  • Asynchronous conditions (24:26)

These sessions provide a comprehensive overview of how async functions work in Swift, including their implementation, memory management, and practical usage in code.