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RxJava Replaying Share

ReplayingShare is an RxJava 3 transformer which combines replay(1), publish(), and refCount() operators.

Unlike traditional combinations of these operators, ReplayingShare caches the last emitted value from the upstream observable or flowable only when one or more downstream subscribers are connected. This allows expensive upstream sources to be shut down when no one is listening while also replaying the last value seen by any subscriber to new ones.

	replayingShare()	replay(1).refCount()	publish().refCount()	replay(1).autoConnect(1)
Disconnects from upstream when there are no subscribers	✅	✅	✅	❌
Replays the latest value to new subscribers when other subscribers are active	✅	✅	❌	✅
Replays the latest value to new subscribers when no other subscribers are active	✅	❌	❌	✅

marble diagram

Usage

Apply with compose to an upstream Observable or Flowable and cache the resulting instance for all new subscribers.

@Singleton class Chart {
  private final Observable<Bitmap> chart;

  @Inject Chart(Observable<List<Data>> data) {
    chart = data.debounce(1, SECONDS)
        .map(list -> bigExpensiveRenderChartToBitmapFunction(list))
        .compose(ReplayingShare.instance());
  }

  Observable<Bitmap> data() {
    return chart;
  }
}

Kotlin users can use the operator via an extension function.

@Singleton class Chart
@Inject constructor(data: Observable<List<Data>>) {
  val chart: Observable<Bitmap> = data.debounce(1, SECONDS)
      .map(list -> bigExpensiveRenderChartToBitmapFunction(list))
      .replayingShare()
}

Note: This operator is designed for composition with infinite or extremely long-lived streams. Any terminal event will clear the cached value.

Download

Gradle:

implementation 'com.jakewharton.rx3:replaying-share:3.0.0'
// Optional:
implementation 'com.jakewharton.rx3:replaying-share-kotlin:3.0.0'

Maven:

<dependency>
  <groupId>com.jakewharton.rx3</groupId>
  <artifactId>replaying-share</artifactId>
  <version>3.0.0</version>
</dependency>
<!-- Optional: -->
<dependency>
  <groupId>com.jakewharton.rx3</groupId>
  <artifactId>replaying-share-kotlin</artifactId>
  <version>3.0.0</version>
</dependency>

Snapshots of the development version are available in Sonatype's snapshots repository.

RxJava 2.x

Gradle:

implementation 'com.jakewharton.rx2:replaying-share:2.2.0'
// Optional:
implementation 'com.jakewharton.rx2:replaying-share-kotlin:2.2.0'

Maven:

<dependency>
  <groupId>com.jakewharton.rx2</groupId>
  <artifactId>replaying-share</artifactId>
  <version>2.2.0</version>
</dependency>
<!-- Optional: -->
<dependency>
  <groupId>com.jakewharton.rx2</groupId>
  <artifactId>replaying-share-kotlin</artifactId>
  <version>2.2.0</version>
</dependency>

RxJava 1.x

Gradle:

implementation 'com.jakewharton.rx:replaying-share:1.0.1'
// Optional:
implementation 'com.jakewharton.rx:replaying-share-kotlin:1.0.1'

Maven:

<dependency>
  <groupId>com.jakewharton.rx</groupId>
  <artifactId>replaying-share</artifactId>
  <version>1.0.1</version>
</dependency>
<!-- Optional: -->
<dependency>
  <groupId>com.jakewharton.rx</groupId>
  <artifactId>replaying-share-kotlin</artifactId>
  <version>1.0.1</version>
</dependency>

License

Copyright 2016 Jake Wharton

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.