Scala未來 - 初學者查詢

Question

下面的代碼沒有預料到什麼。

import scala.concurrent.Future 
import scala.concurrent.ExecutionContext 

object UseFuture extends App 
{ 
    implicit val ec = ExecutionContext.global 
    Future(println { "This should be run in another thread" }) 
    println("Test") 
} 

但我沒能看到未來的輸出。

import scala.concurrent.Future 
import scala.concurrent.ExecutionContext 

object UseFuture extends App 
{ 
    implicit val ec = ExecutionContext.global 
    Future(println { "This should be run in another thread" }) 
} 

一個快速的解釋？

Answer 1

@Thilo是正確的，你的應用程序退出比Future開始執行更快。 基本上，使用Await.result是不是好的做法when you work with Future，所以這個例子只作教育用途:)

import scala.concurrent.{Await, ExecutionContext, Future} 
import scala.concurrent.duration._ 

object UseFuture extends App 
{ 
    implicit val ec = ExecutionContext.global 
    println(s"Current thread: ${Thread.currentThread().getId}") 
    val future = Future(println { s"Thread id in future: ${Thread.currentThread().getId}. This should be run in another thread" }) 

    Await.result(future, 15.seconds) 
    println("Future has been executed") 
}