什麼是F＃異步工作流程的Scala等價物？

Question

什麼是F＃異步工作流的Scala等價物？

例如，如何將F＃代碼片段轉換爲慣用的Scala？

open System.Net 
open Microsoft.FSharp.Control.WebExtensions 

let urlList = [ "Microsoft.com", "http://www.microsoft.com/" 
       "MSDN", "http://msdn.microsoft.com/" 
       "Bing", "http://www.bing.com" 
       ] 

let fetchAsync(name, url:string) = 
    async { 
     try 
      let uri = new System.Uri(url) 
      let webClient = new WebClient() 
      let! html = webClient.AsyncDownloadString(uri) 
      printfn "Read %d characters for %s" html.Length name 
     with 
      | ex -> printfn "%s" (ex.Message); 
    } 

let runAll() = 
    urlList 
    |> Seq.map fetchAsync 
    |> Async.Parallel 
    |> Async.RunSynchronously 
    |> ignore 

runAll() 

Answer 1

你的代碼或多或少直接可以使用轉換爲斯卡拉Futures（帶丟了，雖然一些重要的功能）：

import scala.actors.Futures 
import Futures._ 

val urlList = Map("Microsoft.com" -> "http://www.microsoft.com/", 
       "MSDN" -> "http://msdn.microsoft.com/", 
       "Bing" -> "http://www.bing.com") 


def fetchAsync(name: String, url: String) = future { 
    // lengthy operation simulation 
    Thread.sleep(1000) 
    println("Fetching from %s: %s" format(name, url)) 
} 

def runAll = 
    //Futures.awaitAll( <- if you want to synchronously wait for the futures to complete 
    urlList.map{case (name, url) => fetchAsync(name, url)} 
    //)