/** * 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.observables; import io.reactivex.Observable; import io.reactivex.annotations.Nullable; /** * An {@link Observable} that has been grouped by key, the value of which can be obtained with {@link #getKey()}. * <p> * <em>Note:</em> A {@link GroupedObservable} will cache the items it is to emit until such time as it * is subscribed to. For this reason, in order to avoid memory leaks, you should not simply ignore those * {@code GroupedObservable}s that do not concern you. Instead, you can signal to them that they * may discard their buffers by applying an operator like {@link Observable#take take}{@code (0)} to them. * * @param <K> * the type of the key * @param <T> * the type of the items emitted by the {@code GroupedObservable} * @see Observable#groupBy(io.reactivex.functions.Function) * @see <a href="http://reactivex.io/documentation/operators/groupby.html">ReactiveX documentation: GroupBy</a> */ public abstract class GroupedObservable<K, T> extends Observable<T> { final K key; /** * Constructs a GroupedObservable with the given key. * @param key the key */ protected GroupedObservable(@Nullable K key) { this.key = key; } /** * Returns the key that identifies the group of items emitted by this {@code GroupedObservable}. * * @return the key that the items emitted by this {@code GroupedObservable} were grouped by */ @Nullable public K getKey() { return key; } }