Akka Streams - 如何在圖形中保持輔助接收器的物化值

Question

我有一個返回Flow的函數，其邏輯涉及將圖的一些元素傳遞給作為參數傳遞的輔助Sink 。 我想保留輔助Sink的物化值，這樣我就可以在構造流啟動時對其值進行操作。

這是我正在建設的流程的粗略圖片：

IN ~> (logic: In => Out) ~> Broadcast ~> AuxFilter ~> AuxSink
                                      ~> OutFilter ~> OUT

示例代碼：

case class Incoming()
trait Element
case class Outcoming() extends Element
case class Persistent() extends Element

def flow[Mat](auxSink: Sink[Persistent, Mat]): Flow[Incoming, Outcoming, NotUsed] = {
  val isPersistent = Flow[Element].collect {
    case persistent: Persistent => persistent
  }

  val isRunning = Flow[Element].collect {
    case out: Outcoming => out
  }

  val magicFlow: Flow[Incoming, Element, NotUsed] = Flow[Incoming]
    .map(_ => if (Random.nextBoolean()) Outcoming() else Persistent())

  Flow.fromGraph {
    GraphDSL.create() { implicit b =>
      import GraphDSL.Implicits._

      val magic = b.add(magicFlow)
      val bcast = b.add(Broadcast[Element](2))
      val sink = b.add(isRunning)

                   bcast.out(0) ~> isPersistent ~> auxSink
      magic.out ~> bcast.in
                   bcast.out(1) ~> isRunning ~> sink.in

      FlowShape(magic.in, sink.out)
    }
  }
}

有沒有辦法以某種方式將auxSink的Mat傳遞給最終的Flow ？

謝謝。

Answer 1

回答我自己的問題......

找到了！ Flow.alsoToMat的源Flow.alsoToMat指向了我所需的邏輯 - 訪問輔助圖形的物化值（在我的案例中為auxSink ），必須通過將其作為參數傳遞給GraphDSL.create()將其形狀導入到構造的圖形中GraphDSL.create() 。

def flow[Mat](auxSink: Sink[Persistent, Mat]): Flow[Incoming, Outcoming, Mat] = {
  val isPersistent = ...
  val isRunning = ...
  val magicFlow = ...

  Flow.fromGraph {
    GraphDSL.create(auxSink) { implicit b => aux =>
      import GraphDSL.Implicits._

      val magic = b.add(magicFlow)
      val bcast = b.add(Broadcast[Element](2))
      val sink = b.add(isRunning)

      magic ~> bcast ~> isPersistent ~> aux
               bcast ~> isRunning ~> sink

      FlowShape(magic.in, sink.out)
    }
  }
}