Semaphore
Semaphore is an object that controls access to a resource across multiple execution contexts through use of a traditional counting semaphore.
Unlike DispatchSemaphore, Semaphore does not block any thread. Instead, it suspends Swift concurrency tasks.
Usage
let semaphore = Semaphore(value: 0)
Task {
// Suspends the task until a signal occurs.
await semaphore.wait()
await doSomething()
}
// Resumes the suspended task.
semaphore.signal()
The wait() method has a waitUnlessCancelled() variant that throws CancellationError if the task is cancelled before a signal occurs.
For a nice introduction to semaphores, see The Beauty of Semaphores in Swift ?. The article discusses DispatchSemaphore, but it can easily be ported to Swift concurrency: see the demo playground of this package.
