https://github.com/ReactiveX/RxJava: Reactive Extensions for Java
  • David Karnok 
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.

/**
 * 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;

import io.reactivex.annotations.NonNull;
import io.reactivex.disposables.Disposable;


Provides a mechanism for receiving push-based notification of a valueless completion or an error.

 When a CompletableObserver is subscribed to a CompletableSource through the CompletableSource.subscribe(CompletableObserver) method, the CompletableSource calls onSubscribe(Disposable) with a Disposable that allows disposing the sequence at any time. A well-behaved CompletableSource will call a CompletableObserver's onError(Throwable) or onComplete() method exactly once as they are considered mutually exclusive terminal signals.

 Calling the CompletableObserver's method must happen in a serialized fashion, that is, they must not be invoked concurrently by multiple threads in an overlapping fashion and the invocation pattern must adhere to the following protocol: 
    onSubscribe (onError | onComplete)?


 Subscribing a CompletableObserver to multiple CompletableSources is not recommended. If such reuse happens, it is the duty of the CompletableObserver implementation to be ready to receive multiple calls to its methods and ensure proper concurrent behavior of its business logic. 
 Calling onSubscribe(Disposable) or onError(Throwable) with a null argument is forbidden. 
 The implementations of the onXXX methods should avoid throwing runtime exceptions other than the following cases: 
    

  • If the argument is null, the methods can throw a NullPointerException. Note though that RxJava prevents nulls to enter into the flow and thus there is generally no need to check for nulls in flows assembled from standard sources and intermediate operators. 
    • 

  • If there is a fatal error (such as VirtualMachineError).
    • 



Since:2.0
/**
 * Provides a mechanism for receiving push-based notification of a valueless completion or an error.
 * <p>
 * When a {@code CompletableObserver} is subscribed to a {@link CompletableSource} through the {@link CompletableSource#subscribe(CompletableObserver)} method,
 * the {@code CompletableSource} calls {@link #onSubscribe(Disposable)}  with a {@link Disposable} that allows
 * disposing the sequence at any time. A well-behaved
 * {@code CompletableSource} will call a {@code CompletableObserver}'s {@link #onError(Throwable)}
 * or {@link #onComplete()} method exactly once as they are considered mutually exclusive <strong>terminal signals</strong>.
 * <p>
 * Calling the {@code CompletableObserver}'s method must happen in a serialized fashion, that is, they must not
 * be invoked concurrently by multiple threads in an overlapping fashion and the invocation pattern must
 * adhere to the following protocol:
 * <pre><code>    onSubscribe (onError | onComplete)?</code></pre>
 * <p>
 * Subscribing a {@code CompletableObserver} to multiple {@code CompletableSource}s is not recommended. If such reuse
 * happens, it is the duty of the {@code CompletableObserver} implementation to be ready to receive multiple calls to
 * its methods and ensure proper concurrent behavior of its business logic.
 * <p>
 * Calling {@link #onSubscribe(Disposable)} or {@link #onError(Throwable)} with a
 * {@code null} argument is forbidden.
 * <p>
 * The implementations of the {@code onXXX} methods should avoid throwing runtime exceptions other than the following cases:
 * <ul>
 * <li>If the argument is {@code null}, the methods can throw a {@code NullPointerException}.
 * Note though that RxJava prevents {@code null}s to enter into the flow and thus there is generally no
 * need to check for nulls in flows assembled from standard sources and intermediate operators.
 * </li>
 * <li>If there is a fatal error (such as {@code VirtualMachineError}).</li>
 * </ul>
 * @since 2.0
 */
public interface CompletableObserver {
    
Called once by the Completable to set a Disposable on this instance which
then can be used to cancel the subscription at any time.

Params:
  • d – the Disposable instance to call dispose on for cancellation, not null
/**
     * Called once by the Completable to set a Disposable on this instance which
     * then can be used to cancel the subscription at any time.
     * @param d the Disposable instance to call dispose on for cancellation, not null
     */
    void onSubscribe(@NonNull Disposable d);

    
Called once the deferred computation completes normally.

/**
     * Called once the deferred computation completes normally.
     */
    void onComplete();

    
Called once if the deferred computation 'throws' an exception.

Params:
  • e – the exception, not null.
/**
     * Called once if the deferred computation 'throws' an exception.
     * @param e the exception, not null.
     */
    void onError(@NonNull Throwable e);
}