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/**
* Copyright 2014 Netflix, Inc.
*
* 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 rx.operators;
import java.util.concurrent.atomic.AtomicBoolean;
import rx.Observable;
import rx.Observable.OnSubscribeFunc;
import rx.Observer;
import rx.Subscription;
import rx.subjects.ReplaySubject;
/**
* This method has similar behavior to {@link Observable#replay()} except that this auto-subscribes
* to the source Observable rather than returning a connectable Observable.
*
* 
*
* This is useful with an Observable that you want to cache responses when you can't control the
* subscribe/unsubscribe behavior of all the Observers.
*
* NOTE: You sacrifice the ability to unsubscribe from the origin when you use this operator, so be
* careful not to use this operator on Observables that emit infinite or very large numbers of
* items, as this will use up memory.
*/
public class OperationCache {
public static OnSubscribeFunc cache(final Observable source) {
return new OnSubscribeFunc() {
final AtomicBoolean subscribed = new AtomicBoolean(false);
private final ReplaySubject cache = ReplaySubject.create();
@Override
public Subscription onSubscribe(Observer observer) {
if (subscribed.compareAndSet(false, true)) {
// subscribe to the source once
source.subscribe(cache);
/*
* Note that we will never unsubscribe from 'source' as we want to receive and cache all of its values.
*
* This means this should never be used on an infinite or very large sequence, similar to toList().
*/
}
return cache.subscribe(observer);
}
};
}
}