Scala 从 onComplete 返回值
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Scala return value from onComplete
提问by krzasteka
How can I structure onComplete in Scala to act in this way:
我如何在 Scala 中构建 onComplete 以这种方式执行：
Fig. 1
图。1
{
var x;
if(result.isFailure){
x = foo() // foo is a future
}
if(result.isSuccess){
x = 5
}
bar(x)
}
I thought I could do it this way:
我以为我可以这样做：
Fig. 2
图2
var x = foo onComplete {
case Success(x) => 5
case Failure(t) => foo() //foo is a future
}
bar(x)
But onComplete, onFailure and onSuccess all have Unitas their return type,
但是 onComplete、onFailure 和 onSuccess 都有Unit作为它们的返回类型，
onComplete[U](f: (Try[T]) ? U)(implicit executor: ExecutionContext): Unit
onSuccess[U](pf: PartialFunction[T, U])(implicit executor: ExecutionContext): Unit
onFailure[U](pf: PartialFunction[Throwable, U])(implicit executor: ExecutionContext): Unit
How can I achieve something figure two-ish without using a var?
如何在不使用 var 的情况下实现数字二？
采纳答案by Alexander Tokarev
It is discouraged to block current thread by awaiting a result from a future. Instead, you should call bar() function on processing results of the resultfuture.
不鼓励通过等待未来的结果来阻塞当前线程。相反，您应该调用 bar() 函数来处理result未来的结果。
result map {r =>
5
} recover {
case _ => foo()
} map {r =>
bar(r)
}
回答by Till Rohrmann
You can achieve your goal with
你可以实现你的目标
val x: Future[Int] = foo.map(x => 5).recover{case f => foo()}
// do some more work with your future
x.map(bar(_))
Assuming that foo: Future[_]and foo(): Int.
假设foo: Future[_]和foo(): Int.
