/**
* Copyright 2014 Netflix, Inc.
*
* 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 rx.observables;
import rx.Observable;
import rx.Scheduler;
import rx.Subscriber;
import rx.functions.Func1;
/**
* 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(Func1)
* @see <a href="http://reactivex.io/documentation/operators/groupby.html">ReactiveX documentation: GroupBy</a>
*/
public class GroupedObservable<K, T> extends Observable<T> {
private final K key;
/**
* Converts an {@link Observable} into a {@code GroupedObservable} with a particular key.
*
* @param key
* the key to identify the group of items emitted by this {@code GroupedObservable}
* @param o
* the {@link Observable} to convert
* @return a {@code GroupedObservable} representation of {@code o}, with key {@code key}
*/
public static <K, T> GroupedObservable<K, T> from(K key, final Observable<T> o) {
return new GroupedObservable<K, T>(key, new OnSubscribe<T>() {
@Override
public void call(Subscriber<? super T> s) {
o.unsafeSubscribe(s);
}
});
}
/**
* Returns an Observable that will execute the specified function when a {@link Subscriber} subscribes to
* it.
* <p>
* <img width="640" height="200" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/create.png" alt="">
* <p>
* Write the function you pass to {@code create} so that it behaves as an Observable: It should invoke the
* Subscriber's {@link Subscriber#onNext onNext}, {@link Subscriber#onError onError}, and {@link Subscriber#onCompleted onCompleted} methods appropriately.
* <p>
* A well-formed Observable must invoke either the Subscriber's {@code onCompleted} method exactly once or
* its {@code onError} method exactly once.
* <p>
* See <a href="http://go.microsoft.com/fwlink/?LinkID=205219">Rx Design Guidelines (PDF)</a> for detailed
* information.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code create} does not operate by default on a particular {@link Scheduler}.</dd>
* </dl>
*
* @param <K>
* the type of the key
* @param <T>
* the type of the items that this Observable emits
* @param f
* a function that accepts an {@code Subscriber<T>}, and invokes its {@code onNext}, {@code onError}, and {@code onCompleted} methods as appropriate
* @return a GroupedObservable that, when a {@link Subscriber} subscribes to it, will execute the specified
* function
*/
public final static <K, T> GroupedObservable<K, T> create(K key, OnSubscribe<T> f) {
return new GroupedObservable<K, T>(key, f);
}
protected GroupedObservable(K key, OnSubscribe<T> onSubscribe) {
super(onSubscribe);
this.key = key;
}
/**
* Returns the key that identifies the group of items emited by this {@code GroupedObservable}
*
* @return the key that the items emitted by this {@code GroupedObservable} were grouped by
*/
public K getKey() {
return key;
}
}