/**
* Copyright (c) 2016-present, RxJava Contributors.
*
* 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 io.reactivex.subjects;
import io.reactivex.*;
import io.reactivex.annotations.*;
/**
* Represents an Observer and an Observable at the same time, allowing
* multicasting events from a single source to multiple child Subscribers.
* <p>All methods except the onSubscribe, onNext, onError and onComplete are thread-safe.
* Use {@link #toSerialized()} to make these methods thread-safe as well.
*
* @param <T> the item value type
*/
public abstract class Subject<T> extends Observable<T> implements Observer<T> {
/**
* Returns true if the subject has any Observers.
* <p>The method is thread-safe.
* @return true if the subject has any Observers
*/
public abstract boolean hasObservers();
/**
* Returns true if the subject has reached a terminal state through an error event.
* <p>The method is thread-safe.
* @return true if the subject has reached a terminal state through an error event
* @see #getThrowable()
* &see {@link #hasComplete()}
*/
public abstract boolean hasThrowable();
/**
* Returns true if the subject has reached a terminal state through a complete event.
* <p>The method is thread-safe.
* @return true if the subject has reached a terminal state through a complete event
* @see #hasThrowable()
*/
public abstract boolean hasComplete();
/**
* Returns the error that caused the Subject to terminate or null if the Subject
* hasn't terminated yet.
* <p>The method is thread-safe.
* @return the error that caused the Subject to terminate or null if the Subject
* hasn't terminated yet
*/
@Nullable
public abstract Throwable getThrowable();
/**
* Wraps this Subject and serializes the calls to the onSubscribe, onNext, onError and
* onComplete methods, making them thread-safe.
* <p>The method is thread-safe.
* @return the wrapped and serialized subject
*/
@NonNull
public final Subject<T> toSerialized() {
if (this instanceof SerializedSubject) {
return this;
}
return new SerializedSubject<T>(this);
}
}