Scala 使用具有两个接收器的源并获得一个接收器的结果

我想使用一个具有两个不同接收器的源

简化示例：

val source = Source(1 to 20)

val addSink = Sink.fold[Int, Int](0)(_ + _)
val subtractSink = Sink.fold[Int, Int](0)(_ - _)

val graph = GraphDSL.create() { implicit builder =>
  import GraphDSL.Implicits._

  val bcast = builder.add(Broadcast[Int](2))

  source ~> bcast.in

  bcast.out(0) ~> addSink
  bcast.out(1) ~> subtrackSink

  ClosedShape
}

RunnableGraph.fromGraph(graph).run()

val result: Future[Int] = ???

我需要能够检索addSink的结果。RunnableGraph.fromGraphgraph.run给我的是NotUsed，

---

但是我想得到第一次折叠下沉的结果。有可能吗？

将两个接收器传递给graph builder的create方法，该方法允许您访问它们各自的物化值：

val graph = GraphDSL.create(addSink, subtractSink)((_, _)) { implicit builder =>
  (aSink, sSink) =>
  import GraphDSL.Implicits._

  val bcast = builder.add(Broadcast[Int](2))

  source ~> bcast.in
  bcast.out(0) ~> aSink
  bcast.out(1) ~> sSink
  ClosedShape
}

val (addResult, subtractResult): (Future[Int], Future[Int]) =
  RunnableGraph.fromGraph(graph).run() 

或者，您可以放弃graph DSL并使用：

上面给出了addSink的具体化值。如果要同时获取addSink和subtractSink的物化值，请使用Keep.both：

val result: Future[Int] =
  Source(1 to 20)
    .alsoToMat(addSink)(Keep.right)
    .toMat(subtractSink)(Keep.left)
    .run()

val (addResult, subtractResult): (Future[Int], Future[Int]) =
  Source(1 to 20)
    .alsoToMat(addSink)(Keep.right)
    .toMat(subtractSink)(Keep.both) // <--
    .run()