ProgressFuture

ProgressFuture.swift

class ProgressFuture<Output, Failure: Error> {
    let future: Future<Output, Failure>
    let progress: Progress

    init(_ attemptToFulfill: @escaping (@escaping Future<Output, Failure>.Promise, Progress) -> Void) {
        let progress = Progress()
        self.future = Future { promise in attemptToFulfill(promise, progress) }
        self.progress = progress
    }
}


func example() {
    let progressView = UIProgressView()

    let task = ProgressFuture<String, Error> { promise, progress in
        DispatchQueue.global().async {
            do {
                progress.totalUnitCount = 1000
                for i in 1...1000 {
                    progress.completedUnitCount = Int64(i)

                    if progress.isCancelled {
                        throw GenericError.cancelled
                    }
                }
                promise(.success("Success!"))
            } catch {
                promise(.failure(error))
            }
        }
    }
    // Do something with future
    task.future.replaceError(with: "Failed").sink {
        print($0)
    }

    // And with the progress
    progressView.observedProgress = task.progress

    // Even cancel it
    task.progress.cancel()

}

enum GenericError: Error {
    case cancelled
}