Swift 異步編程庫：Wyrd

Wyrd 是 Swift 異步編程的庫，目標是簡潔和簡單，靈感來源于Promises/A+。包括Swift和Cocoa Touch都沒有提供任何幫助類對于異步編程，除了標準除采取回調success / failure標準函數。 Wyrd試圖用相當簡單的API來解決此問題。

如何安裝

At the moment the most convenient way is to add Wyrd repository as a git submodule to your main repository:

git add submodule add https://github.com/explicitcall/Wyrd.git wyrd

Then add Wyrd.swift file to your project.

CocoaPods package will be added as soon as CocoaPods will support source code in Swift.

如何使用

Essentially, Wyrd instance is a promise, which can be chained with other promises using closures and chaining operators. Wyrd library provides a few wrapper extensions for standard asynchronous Cocoa Touch functions. These extended functions return a promise instead of taking a success/error callback, giving you much clearer code and saving you from a Pyramid of Doom.

Obligatory example (getURLData and FullResponse typealias are provided to you by Wyrd):

let s = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration())
let u1 = NSURL(string: "https://api/endpoint1")
let u2 = NSURL(string: "https://api/endpoint2")
(s.getURLData(u1) => { (full: FullResponse) -> Wyrd<FullResponse> in
  switch full {
  case let (data, response):
    println("data1 length is \(data.length)")
  }
  return s.getURLData(u2)
}).success { (full: FullResponse) in
  switch full {
  case let (data, response):
    println("data2 length is \(data.length)")
  }
}

This code issues two API calls in serial, the second will fail if the first fails.

Wrapping typical asynchronous Cocoa Touch code is fairly easy, just define a method/function which will return a Wyrd instance, which you will be able to chain. You will need to fulfil or reject the promise in the raw callbacks code to indicate when the promise will be able to chain further:

typealias FullResponse = (NSData!, NSURLResponse!)

extension NSURLSession {
  func getURLData(url: NSURL) -> Wyrd<FullResponse> {
    let result = Wyrd<FullResponse>()

    let task = dataTaskWithURL(url) { data, response, error in
      if let e = error {
        result.reject(e)
      } else {
        let tuple = (data, response)
        result.fulfil(tuple)
      }
    }

    task.resume()

    return result
  }
}

項目主頁：http://www.baiduhome.net/lib/view/home/1406168924242