haikusw/queue

A queue for Swift concurrency

Queue

A queue for Swift concurrency

This package exposes a single type: AsyncQueue. Conceptually, AsyncQueue is very similar to a DispatchQueue or OperationQueue. However, unlike these an AsyncQueue can accept async blocks. This exists to more easily enforce ordering across unstructured tasks without requiring explicit dependencies between them.

I've found this helpful when interfacing stateful asynchronous systems with synchronous code.

let queue = AsyncQueue()

queue.addOperation {
    await asyncFunction()
    await anotherAsyncFunction()
}

// This can can also return the underlying Task,
// so you can cancel, or await a value
let task = await queue.addOperation {
    return await makeValue()
}

let value = try await task.value

By default, AsyncQueue will only run one operation at a time. But, it can be configured as a concurrent queue.

let queue = AsyncQueue(attributes: [.concurrent])

// these two may run concurrently
queue.addOperation { await asyncFunction() }
queue.addOperation { await asyncFunction() }

// This will only run once existing operations are complete, and will
// prevent new operations from starting until done
queue.addBarrierOperation {
    await asyncFunction()
}

This package was inspired by Semaphore, which is another concurrency-related synchronization system that I've found very useful.

Contributing and Collaboration

I prefer collaboration, and would love to find ways to work together if you have a similar project.

I prefer indentation with tabs for improved accessibility. But, I'd rather you use the system you want and make a PR than hesitate because of whitespace.

Suggestions and Feedback

I'd love to hear from you! Get in touch via mastodon, an issue, or a pull request.

By participating in this project you agree to abide by the Contributor Code of Conduct.