⚠️ setjmp and longjpm used to implement SwiftCoroutine are generally considered to be undefined behaviour. It's probably a bad idea to use this project for anything other than experimentation. Use at your own risk.

Oh, you're still reading, huh? Alright, I guess I'll get you up to speed. This project is pretty small, so there isn't much to it. Start by adding it as a dependency to your SPM project:

.package(url: "https://github.com/calebkleveter/NIOAsync.git", from: "0.1.0")

Then run swift package update, or feel smug that you have Xcode 11 and wait for it to install.

There are really 2 methods that this package provides. The first is EventLoop.async(_:):

let result: EventLoopFuture<OperationResult> = eventLoop.async {
    return someReallyLongAsyncOperation()
}

This method starts a coroutine and runs the provided closure inside of that coroutine. The value that is returned from the closure is the result that you get in the EventLoopFuture that is returned. The closure also allows you to throw errors. If that happens, your EventLoopFuture will be failed.

The second piece to the puzzel is EventLoopFuture.await():

let user = try User.query(on: database).first().await()

Note that this method is different from the wait method provided by NIO. You can only call it inside the closure of an async call (or inside any other coroutine that you happen to have started). It waits for the future result and returns it, without blocking the current thread because you are in a coroutine.

In the end, your code might look a little like this:

eventLoop.async {
    guard let user = try User.query(on: database).filter(\.$id == id).first().await() else {
        throw Abort(.notFound)
    }
    guard let id = user.id else {
        throw Abort(.internalServerError, reason: "All saved models must have an ID")
    }
    
    return try s3Client.fetch("\(id)/profile-image.png").await()
}

All code, documents, and other resources contained in this repository is under the MIT license agreement.