英文:
How would you time out multiple async requests with Scala's async?
问题
我不了解Scala，但我对它的异步特性（类似于C#）很感兴趣。你想要将这段Go代码翻译成Scala的异步代码，对吗？
import scala.concurrent._
import scala.concurrent.duration._
import scala.concurrent.ExecutionContext.Implicits.global
val c = Promise[Result]()
Future { c.success(Web(query)) }
Future { c.success(Image(query)) }
Future { c.success(Video(query)) }
val timeout = after(80.milliseconds)
var i = 0
while (i < 3) {
Await.ready(c.future, timeout) foreach { result =>
results = results :+ result
}
i += 1
}
这是一个可能的Scala异步代码翻译。它使用了Scala的Future和Promise来实现异步操作，并使用Await.ready和foreach来等待结果。请注意，这只是一种可能的翻译方式，具体实现可能因情况而异。
英文:
I don't know Scala but I am curious about its async feature (similar to C#'s). How would you translate this go code into Scala async?
http://talks.golang.org/2012/concurrency.slide#47
c := make(chan Result)
go func() { c <- Web(query) } ()
go func() { c <- Image(query) } ()
go func() { c <- Video(query) } ()
timeout := time.After(80 * time.Millisecond)
for i := 0; i < 3; i++ {
select {
case result := <-c:
results = append(results, result)
case <-timeout:
fmt.Println("timed out")
return
}
}
return
答案1
得分: 0
这是一个可能的实现草图（未经测试；我不保证这是最佳解决方案）：
// 假设Web/Image/Video函数返回Future[Result]的实例
val f1 = Web(query)
val f2 = Image(query)
val f3 = Video(query)
val t = timeout(80.milliseconds)
// 使用Scala的Future API
val results: Future[Seq[Result]] = for {
r1 <- or(f1)(t)
r2 <- or(f2)(t)
r3 <- or(f3)(t)
} yield (r1.toSeq ++ r2.toSeq ++ r3.toSeq)
// 或者使用async
val results: Future[Seq[Result]] = async {
val r1 = or(f1)(t)
val r2 = or(f2)(t)
val r3 = or(f3)(t)
await(r1).toSeq ++ await(r2).toSeq ++ await(r3).toSeq
}
// or和timeout是下面定义的实用/库函数
def or[T](f1: Future[T])(f2: Future[Option[Nothing]]): Future[Option[T]] =
Future.firstCompletedOf(f1 map Some.apply, f2)
// 创建一个在给定持续时间后成功完成为None的Future
def timeout(d: Duration): Future[Option[Nothing]] = {
val p = Promise[Option[Nothing]]
Scheduler.after(d) { p success None }
p.future
}
希望这可以帮助到你！
英文:
Here's a sketch of how it could be done (untested; I make no claim that this is the best solution):
// I assume that the Web/Image/Video functions return instances of Future[Result]
val f1 = Web(query)
val f2 = Image(query)
val f3 = Video(query)
val t = timeout(80.milliseconds)
// using Scala's Future API
val results: Future[Seq[Result]] = for {
r1 <- or(f1)(t)
r2 <- or(f2)(t)
r3 <- or(f3)(t)
} yield (r1.toSeq ++ r2.toSeq ++ r3.toSeq)
// OR using async
val results: Future[Seq[Result]] = async {
val r1 = or(f1)(t)
val r2 = or(f2)(t)
val r3 = or(f3)(t)
await(r1).toSeq ++ await(r2).toSeq ++ await(r3).toSeq
}
// or and timeout are utility/library functions defined below
def or[T](f1: Future[T])(f2: Future[Option[Nothing]]): Future[Option[T]] =
Future.firstCompletedOf(f1 map Some.apply, f2)
// create a future that will complete successfully with None
// after the given duration passes
def timeout(d: Duration): Future[Option[Nothing]] = {
val p = Promise[Option[Nothing]]
Scheduler.after(d) { p success None }
p.future
}
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