/**
* 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.subjects;
import rx.Observable;
import rx.Observer;
import rx.Subscriber;
/**
* Represents an object that is both an Observable and an Observer.
*/
public abstract class Subject<T, R> extends Observable<R> implements Observer<T> {
protected Subject(OnSubscribe<R> onSubscribe) {
super(onSubscribe);
}
/**
* Indicates whether the {@link Subject} has {@link Observer Observers} subscribed to it.
* @return true if there is at least one Observer subscribed to this Subject, false otherwise
*/
public abstract boolean hasObservers();
/**
* Wraps a {@link Subject} so that it is safe to call its various {@code on} methods from different threads.
* <p>
* When you use an ordinary {@link Subject} as a {@link Subscriber}, you must take care not to call its
* {@link Subscriber#onNext} method (or its other {@code on} methods) from multiple threads, as this could
* lead to non-serialized calls, which violates the Observable contract and creates an ambiguity in the resulting Subject.
* <p>
* To protect a {@code Subject} from this danger, you can convert it into a {@code SerializedSubject} with code
* like the following:
* <p><pre>{@code
* mySafeSubject = myUnsafeSubject.toSerialized();
* }</pre>
*
* @return SerializedSubject wrapping the current Subject
*/
public final SerializedSubject<T, R> toSerialized() {
return new SerializedSubject<T, R>(this);
}
}