Question

如何在Inlet中获取已连接Outlet和FlowShape的实例？请考虑以下示例

def throttleFlow[T](rate: FiniteDuration) = Flow.fromGraph(GraphDSL.create() { implicit builder =>
  import GraphDSL.Implicits._

  val ticker = Source.tick(rate, rate, Unit)

  val zip = builder.add(Zip[T, Unit.type])
  val map = Flow[(T, Unit.type)].map { case (value, _) => value }
  val messageExtractor = builder.add(map)

  val in = Inlet[T]("Req.in")
  val out = Outlet[T]("Req.out")

  out ~> zip.in0
  ticker ~> zip.in1
  zip.out ~> messageExtractor.in

  FlowShape.of(in, messageExtractor.out)
})

当我在Source.via()中使用它时，我得到以下异常

Caused by: java.lang.IllegalArgumentException: requirement failed: The output port [Req.out] is not part of the underlying graph.
    at scala.Predef$.require(Predef.scala:219)
    at akka.stream.impl.StreamLayout$Module$class.wire(StreamLayout.scala:204)

我错过了什么？

Answer 1

in入口和out插座未连接任何内容。这就是为什么有一个例外（不幸的是，这种问题只能在运行时检测到）

你想要一个流，其中唯一的开放入口是其中一个拉链入口（zip.in0，因为zip.in1连接到自动收报机），唯一的开放出口是messageExtractor的输出，那怎么样：

def throttleFlow[T](rate: FiniteDuration) = Flow.fromGraph(GraphDSL.create() { implicit builder =>
  import GraphDSL.Implicits._

  val ticker = Source.tick(rate, rate, ())

  val zip = builder.add(Zip[T, Unit])
  val map = Flow[(T, Unit)].map { case (value, _) => value }
  val messageExtractor = builder.add(map)

  ticker ~> zip.in1
  zip.out ~> messageExtractor.in

  FlowShape.of(zip.in0, messageExtractor.out)
})

如何在FlowShape中获取连接的入口和出口的实例？

1 个答案: