AwaitKit

Have you ever dream to write asynchronous code like its synchronous counterpart?

AwaitKit is a powerful Swift library inspired by the Async/Await specification in ES8 (ECMAScript 2017) which provides a powerful way to write asynchronous code in a sequential manner.

Internally it uses PromiseKit v6.10 to create and manage promises.

Requirements

  • iOS 8.0+
  • Xcode 8.0+
  • Swift 4.0+

Getting Started

If you want have a quick overview of the project take a look to this blog post.

Put simply, write this:

let user = try! await(signIn(username: "Foo", password: "Bar"))
try! await(sendWelcomeMailToUser(user))
try! await(redirectToThankYouScreen())

print("All done!")
Swift

Instead of:

signIn(username: "Foo", password: "Bar")
  .then { user in
    return self.sendWelcomeMailToUser(user)
  }
  .then { _ in
    return self.redirectToThankYouScreen()
  }
  .then { _ in
    print("All done!")
  }
Swift

Or worse, using the completion block imbrication hell style:

signIn(username: "Foo", password: "Bar") { user in
  self.sendWelcomeMailToUser(user) { _ in
    self.redirectToThankYouScreen() { _ in
      print("All done!")
    }
  }
}
Swift

Usage

Async

The async method yields the execution to its closure which will run in a background queue and returns a promise which will be resolved at this end of block.

Here a small example :

func setupNewUser(name: String) -> Promise<User> {  
  return async {
    let newUser = try await(self.createUser(name))
    let friends = try await(self.getFacebookFriends(name))

    newUser.addFriends(friends)

    return newUser
  }
}
Swift

Here the setupNewUser returns a promise with a user as value. If the end of async block is executed the promise will be resolved, otherwise if an error occurred inside the async block the promise will be rejected with the corresponding error.

The async block will catch the error thrown to reject the promise so you don't need to manage the await exceptions. But if necessary, you can:

async {
  do {
    try await(self.loginOrThrown(username: "yannickl"))
  }
  catch {
    print(error)
  }

  try await(self.clearCache())
}
Swift

Await

The await method will executes the given promise or block and await until it resolved or failed.

do {
  let name: String = try await {
    Thread.sleep(forTimeInterval: 0.2)

    if Int(arc4random_uniform(2) + 1) % 2 == 0 {
      return "yannickl"
    }
    else {
      throw NSError()
    }
  }

  print(name)
}
catch {
  print(error)
}
Swift

Custom queues

The async and await methods runs by default on a background concurrent queue. Of course, you can choose your own queues and call the following methods:

DispatchQueue.global(qos: .default).ak.async {

}

try DispatchQueue.global(qos: .default).ak.await {

}
Swift

When you use these methods and you are doing asynchronous, be careful to do nothing in the main thread, otherwise you risk to enter in a deadlock situation.

Installation

The recommended approach to use AwaitKit in your project is using the CocoaPods package manager, as it provides flexible dependency management and dead simple installation.

CocoaPods

Install CocoaPods if not already available:

$ [sudo] gem install cocoapods
$ pod setup
Bash

Go to the directory of your Xcode project, and Create and Edit your Podfile and add AwaitKit:

$ cd /path/to/MyProject
$ touch Podfile
$ edit Podfile
source 'https://github.com/CocoaPods/Specs.git'
platform :ios, '8.0'
pod 'AwaitKit', '~> 5.2.0'
Bash

Install into your project:

$ pod install
Bash

If CocoaPods did not find the PromiseKit 6.10 dependency execute this command:

$ pod repo update
Bash

Open your project in Xcode from the .xcworkspace file (not the usual project file)

$ open MyProject.xcworkspace
Bash

Swift Package Manager

You can use The Swift Package Manager to install AwaitKit by adding the proper description to your Package.swift file:

import PackageDescription

let package = Package(
    name: "YOUR_PROJECT_NAME",
    dependencies: [
        .Package(url: "https://github.com/yannickl/AwaitKit.git")
    ]
)
Swift

Note that the Swift Package Manager is still in early design and development, for more information checkout its GitHub Page.

Carthage

Carthage is a decentralized dependency manager that builds your dependencies and provides you with binary frameworks.

You can install Carthage with Homebrew using the following command:

$ brew update
$ brew install carthage
Bash

To integrate AwaitKit into your Xcode project using Carthage, specify it in your Cartfile:

github "yannickl/AwaitKit" ~> 5.2.0
Ogdl

Run carthage update to build the framework and drag the built AwaitKit.framework into your Xcode project.

Manually

Download the project and copy the AwaitKit folder into your project to use it in. Note that you also need to download the PromiseKit v6.7 library and import it to your project.

Contribution

Contributions are welcomed and encouraged ♡.

Contact

Yannick Loriot

License (MIT)

Copyright (c) 2016-present - Yannick Loriot

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

GitHub

https://github.com/yannickl/AwaitKit