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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.Iterator;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;
import rx.Observable;
import rx.Observer;
import rx.exceptions.Exceptions;
/**
* Returns an Iterable that always returns the item most recently emitted by an Observable, or a
* seed value if no item has yet been emitted.
*
* 
*/
public final class OperationMostRecent {
public static Iterable mostRecent(final Observable source, final T initialValue) {
return new Iterable() {
@Override
public Iterator iterator() {
MostRecentObserver mostRecentObserver = new MostRecentObserver(initialValue);
final MostRecentIterator nextIterator = new MostRecentIterator(mostRecentObserver);
source.subscribe(mostRecentObserver);
return nextIterator;
}
};
}
private static class MostRecentIterator implements Iterator {
private final MostRecentObserver observer;
private MostRecentIterator(MostRecentObserver observer) {
this.observer = observer;
}
@Override
public boolean hasNext() {
return !observer.isCompleted();
}
@Override
public T next() {
if (observer.getThrowable() != null) {
throw Exceptions.propagate(observer.getThrowable());
}
return observer.getRecentValue();
}
@Override
public void remove() {
throw new UnsupportedOperationException("Read only iterator");
}
}
private static class MostRecentObserver implements Observer {
private final AtomicBoolean completed = new AtomicBoolean(false);
private final AtomicReference value;
private final AtomicReference exception = new AtomicReference();
private MostRecentObserver(T value) {
this.value = new AtomicReference(value);
}
@Override
public void onCompleted() {
completed.set(true);
}
@Override
public void onError(Throwable e) {
exception.set(e);
}
@Override
public void onNext(T args) {
value.set(args);
}
private boolean isCompleted() {
return completed.get();
}
private Throwable getThrowable() {
return exception.get();
}
private T getRecentValue() {
return value.get();
}
}
}