monifu.reactive.internals.operators.foldLeft.scala Maven / Gradle / Ivy
/*
* Copyright (c) 2014-2015 by its authors. Some rights reserved.
* See the project homepage at: http://www.monifu.org
*
* 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.internals.operators
import monifu.reactive.Ack.{Cancel, Continue}
import monifu.reactive.{Observable, Ack, Observer}
import scala.concurrent.Future
import scala.util.control.NonFatal
private[reactive] object foldLeft {
/**
* Implementation for [[Observable.foldLeft]].
*/
def apply[T, R](source: Observable[T], initial: R)(op: (R, T) => R): Observable[R] =
Observable.create[R] { subscriber =>
implicit val s = subscriber.scheduler
val observer = subscriber.observer
source.onSubscribe(new Observer[T] {
private[this] var state = initial
def onNext(elem: T): Future[Ack] = {
// See Section 6.4. in the Rx Design Guidelines:
// Protect calls to user code from within an operator
try {
state = op(state, elem)
Continue
}
catch {
case NonFatal(ex) =>
onError(ex)
Cancel
}
}
def onComplete() = {
observer.onNext(state)
observer.onComplete()
}
def onError(ex: Throwable) = {
observer.onError(ex)
}
})
}
}