/**
* 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:
* <pre>
* Single<Integer> single = Observable.range(1, 10).reduce((a, b) -> a + b);
* Observable<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.
* <p>The implementation should handle the necessary RxJavaPlugins wrapping.
* @return the Observable instance
*/
Observable<T> fuseToObservable();
}