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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.internal.operators;
import java.util.NoSuchElementException;
import rx.*;
/**
* Allows conversion of an Observable to a Single ensuring that exactly one item is emitted - no more and no less.
* Also forwards errors as appropriate.
* @param the value type
*/
public class OnSubscribeSingle implements Single.OnSubscribe {
private final Observable observable;
public OnSubscribeSingle(Observable observable) {
this.observable = observable;
}
@Override
public void call(final SingleSubscriber child) {
Subscriber parent = new Subscriber() {
private boolean emittedTooMany;
private boolean itemEmitted;
private T emission;
@Override
public void onStart() {
// We request 2 here since we need 1 for the single and 1 to check that the observable
// doesn't emit more than one item
request(2);
}
@Override
public void onCompleted() {
if (emittedTooMany) {
// Don't need to do anything here since we already sent an error downstream
} else {
if (itemEmitted) {
child.onSuccess(emission);
} else {
child.onError(new NoSuchElementException("Observable emitted no items"));
}
}
}
@Override
public void onError(Throwable e) {
child.onError(e);
unsubscribe();
}
@Override
public void onNext(T t) {
if (itemEmitted) {
emittedTooMany = true;
child.onError(new IllegalArgumentException("Observable emitted too many elements"));
unsubscribe();
} else {
itemEmitted = true;
emission = t;
}
}
};
child.add(parent);
observable.unsafeSubscribe(parent);
}
public static OnSubscribeSingle create(Observable observable) {
return new OnSubscribeSingle(observable);
}
}