obuchiyuki/promise

Features

• Familiar chaining (map, flatMap, catch, finally, timeout, wait, and more)
• Value and error transformation operators
• Racing and zipping helpers such as merge, combine, combineAll
• Swift Concurrency bridges (promise.value, detached tasks, Task.promise)
• Combine bridges (promise.publisher() and Publisher.firstValue())
• GCD helpers for running work on queues or delaying delivery
• URLSession convenience wrappers (session.fetch, session.data)
• Built‑in debug aids (print, measureInterval, breakpointOnError)
• Optional resolver/rejector objects that raise on deinit if unused
• Fully Sendable on supported platforms
• Requires no external dependencies

Requirements

| Platform | Minimum Version | | -------- | --------------- | | iOS | 12.0 | | macOS | 10.15 | | tvOS | 12.0 | | watchOS | 4.0 |

Swift 6 or later and Xcode 17 are recommended.

Installation

Swift Package Manager

Add the package URL in Xcode:

https://github.com/ObuchiYuki/Promise.git

or add it to dependencies in Package.swift:

.package(url: "https://github.com/ObuchiYuki/Promise.git", from: "1.0.0")

Then declare a target dependency:

.target(
    name: "YourApp",
    dependencies: ["Promise"]
)

Quick start

// Wrap URLSession into a promise
func loadImage(from url: URL) -> Promise<UIImage, Error> {
    URLSession.shared.data(for: url)
        .map(UIImage.init(data:))
        .tryMap { image -> UIImage in
            guard let image else { throw URLError(.cannotDecodeContentData) }
            return image
        }
}

// Consume with Combine‑style operators
loadImage(from: url)
    .timeout(5)
    .peek { print("loaded image with size \($0.size)") }
    .catch { print("failed:", $0) }

// Or with async/await
let image = try await loadImage(from: url).value

Documentation

License

Promise is released under the MIT License. See the LICENSE file for details.

Package Metadata

Repository: obuchiyuki/promise

Default branch: main

README: README.md