monifu.reactive.observers.SynchronousObserver.scala Maven / Gradle / Ivy

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/*
 * Copyright (c) 2014-2016 by its authors. Some rights reserved.
 * See the project homepage at: https://monix.io
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package monifu.reactive.observers

import monifu.reactive.Observer
import monifu.reactive.Ack

/**
 * A `SynchronousObserver` is an [[Observer]] that signals demand
 * to upstream synchronously (i.e. the upstream observable doesn't need to
 * wait on a `Future` in order to decide whether to send the next event
 * or not).
 *
 * Can be used for optimizations.
 */
trait SynchronousObserver[-T] extends Observer[T] {
  /**
   * Returns either a [[monifu.reactive.Ack.Continue Continue]] or a
   * [[monifu.reactive.Ack.Cancel Cancel]], in response to an `elem` event
   * being received.
   */
  def onNext(elem: T): Ack
}