什么是Scala等同于F#的异步工作流？
发布时间：2020-12-16 09:19:55 所属栏目：安全 来源：网络整理
导读：什么是Scala等同于F#的异步工作流？ 例如,F#代码段如何转换成惯用的Scala？ open System.Netopen Microsoft.FSharp.Control.WebExtensionslet urlList = [ "Microsoft.com","http://www.microsoft.com/" "MSDN","http://msdn.microsoft.com/" "Bing","http:/
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什么是Scala等同于F#的异步工作流？
例如,F#代码段如何转换成惯用的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()
解决方法
您的代码或多或少直接可以翻译成Scala使用Futures(有一些重要功能丢失,虽然)：
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)}
//)
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