Understanding tasks

Tasks are “units of work” that can run concurrently, and they are a higher-level abstraction over threads, queues, and similar concurrency primitives. Essentially, in Swift, a task is simply a piece of work that can run in parallel with other tasks. In contrast to threads and queues, tasks are managed by the Swift runtime and not by the operating system. This makes them more lightweight and efficient. Moreover, this allows structured concurrency to be backported by Apple to iOS 13 just by updating Xcode, as iOS 13 did not offer this feature when it was first introduced.

Beware that in the first iterations of structured concurrency, you were supposed to be able to declare a task just by using the async keyword, followed by do/catch. The async keyword followed by do/catch syntax method has been replaced with task initialization. You won’t find that in this book; if you happen to find it in old code, just replace async with an appropriate task...