如何转换Rx可观察到的播放枚举器

Question

我使用其本机枚举器构造成功设置了一个WebSocket，调用一些返回字符串的代码：

def operationStatusFeed = WebSocket.using[String] { implicit request =>
  val in = Iteratee.ignore[String]
  val out = Enumerator.repeatM {
   Promise.timeout(operation, 3 seconds)
  }
  (in, out)
}

.

现在我希望我的operation函数返回一个字符串而不是字符串，而且我想在进入后立即输出任何字符串。如何将其映射到rx.lang.scala.Observable[String]？

Answer 1

可以使用Bryan Gilbert的隐式转换。这将完全正常，但要小心使用更新版本的Bryan Gilbert的转换！从Jeroen Kransen（这不好！）中从未呼吁取消订阅。

  /*
   * Observable to Enumerator
   */
  implicit def observable2Enumerator[T](obs: Observable[T]): Enumerator[T] = {
    // unicast create a channel where you can push data and returns an Enumerator
    Concurrent.unicast { channel =>
      val subscription = obs.subscribe(new ChannelObserver(channel))
      val onComplete = { () => subscription.unsubscribe }
      val onError = { (_: String, _: Input[T]) => subscription.unsubscribe }
      (onComplete, onError)
    }
  }

  class ChannelObserver[T](channel: Channel[T]) extends rx.lang.scala.Observer[T] {
    override def onNext(elem: T): Unit = channel.push(elem)
    override def onCompleted(): Unit = channel.end()
    override def onError(e: Throwable): Unit = channel.end(e)
  }

.

要完成，这是从枚举器转换到可观察到的：

  /*
   * Enumerator to Observable
   */
  implicit def enumerator2Observable[T](enum: Enumerator[T]): Observable[T] = {
    // creating the Observable that we return
    Observable({ observer: Observer[T] =>
      // keeping a way to unsubscribe from the observable
      var cancelled = false

      // enumerator input is tested with this predicate
      // once cancelled is set to true, the enumerator will stop producing data
      val cancellableEnum = enum through Enumeratee.breakE[T](_ => cancelled)

      // applying iteratee on producer, passing data to the observable
      cancellableEnum (
        Iteratee.foreach(observer.onNext(_))
      ).onComplete { // passing completion or error to the observable
        case Success(_) => observer.onCompleted()
        case Failure(e) => observer.onError(e)
      }

      // unsubscription will change the var to stop the enumerator above via the breakE function
      new Subscription { override def unsubscribe() = { cancelled = true } }
    })
  }

.

---

rx for websockets在play

中 另一方面，您可以评论您在播放中处理迭代和枚举器的大部分时间是当您使用WebSockets（如您在此处）。我们都同意迭代真的不太直观，观察到，这可能是你在播放项目中使用Rx的原因。

从该观察开始，我构建了一个名为 WidgetManager 的库，它确实如此：RX集成在播放中摆脱迭代操纵。

使用该库，您的代码可以简单地是：

def operationStatusFeed = WebSocket.using[String] { implicit request =>

  // you can optionally give a function to process data from the client (processClientData)
  // and a function to execute when connection is closed (onClientClose)
  val w = new WidgetManager()

  w.addObservable("op", operation)

  // subscribe to it and push data in the socket to the client (automatic JS callback called)
  w.subscribePush("op")

  // deals with Iteratees and Enumerators for you and returns what's needed
  w.webSocket
}

.

图书馆在这里on github： rxplay （欢迎贡献）

Answer 2

我做了这个解决方案，它受到了 Brian Gilbert ：

class ChannelObserver[T](chan: Channel[T]) extends Observer[T] {
  override def onNext(arg: T): Unit = chan.push(arg)
  override def onCompleted(): Unit = chan.end()
  override def onError(e: Throwable): Unit = chan.end(e)
  override val asJavaObserver: rx.Observer[T] = new rx.Observer[T] {
    def onCompleted() {
      chan.end()
    }

    def onError(e: Throwable) {
      chan.end(e)
    }

    def onNext(arg: T) {
      chan.push(arg)
    }
  }
}

implicit def observable2Enumerator[T](obs: Observable[T]): Enumerator[T] = {
  Concurrent.unicast[T](onStart = { chan =>
      obs.subscribe(new ChannelObserver(chan))
  })
}

.

隐式函数将可观察到枚举器转换为枚举器，而无需任何其他代码。