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.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.functions.Cancellable;


Abstraction over an RxJava MaybeObserver that allows associating a resource with it. 

All methods are safe to call from multiple threads, but note that there is no guarantee
whose terminal event will win and get delivered to the downstream.

 Calling onSuccess(Object) or onComplete() multiple times has no effect. Calling onError(Throwable) multiple times or after the other two will route the exception into the global error handler via RxJavaPlugins.onError(Throwable). 
 The emitter allows the registration of a single resource, in the form of a Disposable or Cancellable via setDisposable(Disposable) or setCancellable(Cancellable) respectively. The emitter implementations will dispose/cancel this instance when the downstream cancels the flow or after the event generator logic calls onSuccess(Object), onError(Throwable), onComplete() or when tryOnError(Throwable) succeeds. 
 Only one Disposable or Cancellable object can be associated with the emitter at a time. Calling either set method will dispose/cancel any previous object. If there is a need for handling multiple resources, one can create a CompositeDisposable and associate that with the emitter instead. 
 The Cancellable is logically equivalent to Disposable but allows using cleanup logic that can throw a checked exception (such as many close() methods on Java IO components). Since the release of resources happens after the terminal events have been delivered or the sequence gets cancelled, exceptions throw within Cancellable are routed to the global error handler via RxJavaPlugins.onError(Throwable). 
Type parameters:
  • <T> – the value type to emit
/**
 * Abstraction over an RxJava {@link MaybeObserver} that allows associating
 * a resource with it.
 * <p>
 * All methods are safe to call from multiple threads, but note that there is no guarantee
 * whose terminal event will win and get delivered to the downstream.
 * <p>
 * Calling {@link #onSuccess(Object)} or {@link #onComplete()} multiple times has no effect.
 * Calling {@link #onError(Throwable)} multiple times or after the other two will route the
 * exception into the global error handler via {@link io.reactivex.plugins.RxJavaPlugins#onError(Throwable)}.
 * <p>
 * The emitter allows the registration of a single resource, in the form of a {@link Disposable}
 * or {@link Cancellable} via {@link #setDisposable(Disposable)} or {@link #setCancellable(Cancellable)}
 * respectively. The emitter implementations will dispose/cancel this instance when the
 * downstream cancels the flow or after the event generator logic calls {@link #onSuccess(Object)},
 * {@link #onError(Throwable)}, {@link #onComplete()} or when {@link #tryOnError(Throwable)} succeeds.
 * <p>
 * Only one {@code Disposable} or {@code Cancellable} object can be associated with the emitter at
 * a time. Calling either {@code set} method will dispose/cancel any previous object. If there
 * is a need for handling multiple resources, one can create a {@link io.reactivex.disposables.CompositeDisposable}
 * and associate that with the emitter instead.
 * <p>
 * The {@link Cancellable} is logically equivalent to {@code Disposable} but allows using cleanup logic that can
 * throw a checked exception (such as many {@code close()} methods on Java IO components). Since
 * the release of resources happens after the terminal events have been delivered or the sequence gets
 * cancelled, exceptions throw within {@code Cancellable} are routed to the global error handler via
 * {@link io.reactivex.plugins.RxJavaPlugins#onError(Throwable)}.
 *
 * @param <T> the value type to emit
 */
public interface MaybeEmitter<T> {

    
Signal a success value.

Params:
  • t – the value, not null
/**
     * Signal a success value.
     * @param t the value, not null
     */
    void onSuccess(@NonNull T t);

    
Signal an exception.

Params:
  • t – the exception, not null
/**
     * Signal an exception.
     * @param t the exception, not null
     */
    void onError(@NonNull Throwable t);

    
Signal the completion.

/**
     * Signal the completion.
     */
    void onComplete();

    
Sets a Disposable on this emitter; any previous Disposable or Cancellable will be disposed/cancelled. 
Params:
  • d – the disposable, null is allowed
/**
     * Sets a Disposable on this emitter; any previous {@link Disposable}
     * or {@link Cancellable} will be disposed/cancelled.
     * @param d the disposable, null is allowed
     */
    void setDisposable(@Nullable Disposable d);

    
Sets a Cancellable on this emitter; any previous Disposable or Cancellable will be disposed/cancelled. 
Params:
  • c – the cancellable resource, null is allowed
/**
     * Sets a Cancellable on this emitter; any previous {@link Disposable}
     * or {@link Cancellable} will be disposed/cancelled.
     * @param c the cancellable resource, null is allowed
     */
    void setCancellable(@Nullable Cancellable c);

    
Returns true if the downstream disposed the sequence or the emitter was terminated via onSuccess(Object), onError(Throwable), onComplete or a successful tryOnError(Throwable). 
This method is thread-safe.

Returns:true if the downstream disposed the sequence or the emitter was terminated
/**
     * Returns true if the downstream disposed the sequence or the
     * emitter was terminated via {@link #onSuccess(Object)}, {@link #onError(Throwable)},
     * {@link #onComplete} or a
     * successful {@link #tryOnError(Throwable)}.
     * <p>This method is thread-safe.
     * @return true if the downstream disposed the sequence or the emitter was terminated
     */
    boolean isDisposed();

    
Attempts to emit the specified Throwable error if the downstream hasn't cancelled the sequence or is otherwise terminated, returning false if the emission is not allowed to happen due to lifecycle restrictions. 
 Unlike onError(Throwable), the RxJavaPlugins.onError is not called if the error could not be delivered. 
History: 2.1.1 - experimental

Params:
  • t – the throwable error to signal if possible
Returns:true if successful, false if the downstream is not able to accept further
events
Since:2.2
/**
     * Attempts to emit the specified {@code Throwable} error if the downstream
     * hasn't cancelled the sequence or is otherwise terminated, returning false
     * if the emission is not allowed to happen due to lifecycle restrictions.
     * <p>
     * Unlike {@link #onError(Throwable)}, the {@code RxJavaPlugins.onError} is not called
     * if the error could not be delivered.
     * <p>History: 2.1.1 - experimental
     * @param t the throwable error to signal if possible
     * @return true if successful, false if the downstream is not able to accept further
     * events
     * @since 2.2
     */
    boolean tryOnError(@NonNull Throwable t);
}