Introduction
IdentifiableContinuation is a lightweight wrapper around CheckedContinuation and UnsafeContinuation that conforms to Identifiable and includes an easy to use cancellation handler with the id.
Installation
IdentifiableContinuation can be installed by using Swift Package Manager.
Note: IdentifiableContinuation requires Swift 5.7 on Xcode 14+. It runs on iOS 13+, tvOS 13+, macOS 10.15+, Linux and Windows.
To install using Swift Package Manager, add this to the dependencies: section in your Package.swift file:
.package(url: "https://github.com/swhitty/IdentifiableContinuation.git", .upToNextMajor(from: "0.0.1"))Usage
Usage is similar to existing continuations:
let val: String = await withIdentifiableContinuation {
$0.resume(returning: "bar")
}The continuation includes an id that can be attached to an asynchronous task enabling the onCancel handler to cancel it.
let val: String? = await withIdentifiableContinuation { continuation in
foo.startTask(for: continuation.id) { result
continuation.resume(returning: result)
}
} onCancel: { id in
foo.cancelTask(for: id)
}async closures can be used making it easy to store the continuations within an actor:
let val: String? = await withIdentifiableContinuation {
await someActor.insertContinuation($0)
} onCancel: {
await someActor.cancelContinuation(for: $0)
}Note: The
onCancel:handler is guaranteed to be called after the continuation body even if the task is already cancelled. Manually checkTask.isCancelledbefore creating the continuation to prevent performing unrequired work.
Checked/UnsafeContinuation
IdentifiableContinuation internally stores either a checked or unsafe continuation.
CheckedContinuation is used by the default methods:
withIdentifiableContinuationwithThrowingIdentifiableContinuation
UnsafeContinuation is used by the unsafe methods:
withIdentifiableUnsafeContinuationwithThrowingIdentifiableUnsafeContinuation
Credits
IdentifiableContinuation is primarily the work of Simon Whitty.