/**

* 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;

import rx.subscriptions.CompositeSubscription;

/**

* Provides a mechanism for receiving push-based notifications.

* <p>

* After an Observer calls an {@link Observable}'s <code>Observable.subscribe</code> method, the {@link Observable} calls the

* Observer's <code>onNext</code> method to provide notifications. A well-behaved {@link Observable} will call an Observer's

* <code>onCompleted</code> closure exactly once or the Observer's <code>onError</code> closure exactly once.

* <p>

* For more information see the <a href="https://github.com/Netflix/RxJava/wiki/Observable">RxJava Wiki</a>

*

* @param <T>

*/

public abstract class Observer<T> implements Subscription {

private final CompositeSubscription cs;

protected Observer(CompositeSubscription cs) {

if (cs == null) {

throw new IllegalArgumentException("The CompositeSubscription can not be null");

}

this.cs = cs;

}

protected Observer() {

this(new CompositeSubscription());

}

protected Observer(Observer<?> op) {

this(op.cs);

}

/**

* Notifies the Observer that the {@link Observable} has finished sending push-based notifications.

* <p>

* The {@link Observable} will not call this closure if it calls <code>onError</code>.

*/

public abstract void onCompleted();

/**

* Notifies the Observer that the {@link Observable} has experienced an error condition.

* <p>

* If the {@link Observable} calls this closure, it will not thereafter call <code>onNext</code> or <code>onCompleted</code>.

*

* @param e

*/

public abstract void onError(Throwable e);

/**

* Provides the Observer with new data.

* <p>

* The {@link Observable} calls this closure 1 or more times, unless it calls <code>onError</code> in which case this closure may never be called.

* <p>

* The {@link Observable} will not call this closure again after it calls either <code>onCompleted</code> or <code>onError</code>.

*

* @param args

*/

public abstract void onNext(T t);

/**

* Used to register an unsubscribe callback.

*/

public final void add(Subscription s) {

cs.add(s);

}

@Override

public final void unsubscribe() {

cs.unsubscribe();

}

public final boolean isUnsubscribed() {

return cs.isUnsubscribed();

}

}