120 lines
2.8 KiB
Scala
120 lines
2.8 KiB
Scala
package docs.stream.cookbook
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import akka.stream.scaladsl.{ Sink, Source }
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import akka.stream.testkit.StreamTestKit
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import akka.stream.testkit.StreamTestKit.{ SubscriberProbe, PublisherProbe }
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import scala.concurrent.duration._
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object HoldOps {
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//#hold-version-1
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import akka.stream.stage._
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class HoldWithInitial[T](initial: T) extends DetachedStage[T, T] {
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private var currentValue: T = initial
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override def onPush(elem: T, ctx: DetachedContext[T]): UpstreamDirective = {
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currentValue = elem
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ctx.pull()
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}
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override def onPull(ctx: DetachedContext[T]): DownstreamDirective = {
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ctx.push(currentValue)
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}
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}
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//#hold-version-1
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//#hold-version-2
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import akka.stream.stage._
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class HoldWithWait[T] extends DetachedStage[T, T] {
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private var currentValue: T = _
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private var waitingFirstValue = true
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override def onPush(elem: T, ctx: DetachedContext[T]): UpstreamDirective = {
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currentValue = elem
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waitingFirstValue = false
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if (ctx.isHolding) ctx.pushAndPull(currentValue)
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else ctx.pull()
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}
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override def onPull(ctx: DetachedContext[T]): DownstreamDirective = {
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if (waitingFirstValue) ctx.hold()
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else ctx.push(currentValue)
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}
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}
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//#hold-version-2
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}
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class RecipeHold extends RecipeSpec {
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import HoldOps._
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"Recipe for creating a holding element" must {
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"work for version 1" in {
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val pub = PublisherProbe[Int]()
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val sub = SubscriberProbe[Int]()
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val source = Source(pub)
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val sink = Sink(sub)
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source.transform(() => new HoldWithInitial(0)).to(sink).run()
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val manualSource = new StreamTestKit.AutoPublisher(pub)
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val subscription = sub.expectSubscription()
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sub.expectNoMsg(100.millis)
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subscription.request(1)
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sub.expectNext(0)
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subscription.request(1)
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sub.expectNext(0)
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manualSource.sendNext(1)
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manualSource.sendNext(2)
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subscription.request(2)
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sub.expectNext(2)
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sub.expectNext(2)
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manualSource.sendComplete()
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subscription.request(1)
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sub.expectComplete()
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}
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"work for version 2" in {
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val pub = PublisherProbe[Int]()
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val sub = SubscriberProbe[Int]()
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val source = Source(pub)
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val sink = Sink(sub)
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source.transform(() => new HoldWithWait).to(sink).run()
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val manualSource = new StreamTestKit.AutoPublisher(pub)
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val subscription = sub.expectSubscription()
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sub.expectNoMsg(100.millis)
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subscription.request(1)
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sub.expectNoMsg(100.millis)
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manualSource.sendNext(1)
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sub.expectNext(1)
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manualSource.sendNext(2)
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manualSource.sendNext(3)
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subscription.request(2)
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sub.expectNext(3)
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sub.expectNext(3)
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manualSource.sendComplete()
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subscription.request(1)
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sub.expectComplete()
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}
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}
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}
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