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.internal.fuseable;

import io.reactivex.Observable;


Interface indicating a operator implementation can be macro-fused back to Observable in case
the operator goes from Observable to some other reactive type and then the sequence calls
for toObservable again:

Single<Integer> single = Observable.range(1, 10).reduce((a, b) -> a + b);
Observable<Integer> observable = single.toObservable();

 The Single.toObservable() will check for this interface and call the fuseToObservable() to return an Observable which could be the Observable-specific implementation of reduce(BiFunction). 

This causes a slight overhead in assembly time (1 instanceof check, 1 operator allocation and 1 dropped
operator) but does not incur the conversion overhead at runtime.

Type parameters:
  • <T> – the value type
/**
 * Interface indicating a operator implementation can be macro-fused back to Observable in case
 * the operator goes from Observable to some other reactive type and then the sequence calls
 * for toObservable again:
 * <pre>
 * Single&lt;Integer> single = Observable.range(1, 10).reduce((a, b) -> a + b);
 * Observable&lt;Integer> observable = single.toObservable();
 * </pre>
 *
 * The {@code Single.toObservable()} will check for this interface and call the {@link #fuseToObservable()}
 * to return an Observable which could be the Observable-specific implementation of reduce(BiFunction).
 * <p>
 * This causes a slight overhead in assembly time (1 instanceof check, 1 operator allocation and 1 dropped
 * operator) but does not incur the conversion overhead at runtime.
 *
 * @param <T> the value type
 */
public interface FuseToObservable<T> {

    
Returns a (direct) Observable for the operator.

The implementation should handle the necessary RxJavaPlugins wrapping.

Returns:the Observable instance
/**
     * Returns a (direct) Observable for the operator.
     * <p>The implementation should handle the necessary RxJavaPlugins wrapping.
     * @return the Observable instance
     */
    Observable<T> fuseToObservable();
}