/** * 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 org.reactivestreams.Subscriber; /** * Interface to map/wrap a downstream subscriber to an upstream subscriber. * * @param <Downstream> the value type of the downstream * @param <Upstream> the value type of the upstream */ public interface FlowableOperator<Downstream, Upstream> { /** * Applies a function to the child Subscriber and returns a new parent Subscriber. * @param observer the child Subscriber instance * @return the parent Subscriber instance * @throws Exception on failure */ @NonNull Subscriber<? super Upstream> apply(@NonNull Subscriber<? super Downstream> observer) throws Exception; }