/** * 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.*; /** * Interface to compose Observables. * * @param <Upstream> the upstream value type * @param <Downstream> the downstream value type */ public interface ObservableTransformer<Upstream, Downstream> { /** * Applies a function to the upstream Observable and returns an ObservableSource with * optionally different element type. * @param upstream the upstream Observable instance * @return the transformed ObservableSource instance */ @NonNull ObservableSource<Downstream> apply(@NonNull Observable<Upstream> upstream); }