/**
* 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.internal.operators;
import java.util.*;
import rx.
Observable.
Operator;
import rx.
Subscriber;
import rx.exceptions.
Exceptions;
import rx.internal.producers.
SingleDelayedProducer;
/**
* Returns an {@code Observable} that emits a single item, a list composed of all the items emitted by the
* source {@code Observable}.
* <p>
* <img width="640" height="305" src="https://raw.githubusercontent.com/wiki/ReactiveX/RxJava/images/rx-operators/toList.png" alt="">
* <p>
* Normally, an {@code Observable} that returns multiple items will do so by invoking its subscriber's
* {@link Subscriber#onNext onNext} method for each such item. You can change this behavior, instructing the
* {@code Observable} to compose a list of all of these multiple items and then to invoke the subscriber's
* {@code onNext} method once, passing it the entire list, by using this operator.
* <p>
* Be careful not to use this operator on {@code Observable}s that emit infinite or very large numbers of items,
* as you do not have the option to unsubscribe.
* @param <T> the value type of the input and the output list's items
*/
public final class
OperatorToObservableList<T> implements
Operator<
List<T>, T> {
/** Lazy initialization via inner-class holder. */
static final class
Holder {
/** A singleton instance. */
static final
OperatorToObservableList<
Object>
INSTANCE = new
OperatorToObservableList<
Object>();
}
/**
* @param <T> the value type of the input and the output list's items
* @return a singleton instance of this stateless operator.
*/
@
SuppressWarnings({ "unchecked" })
public static <T>
OperatorToObservableList<T>
instance() {
return (
OperatorToObservableList<T>)
Holder.
INSTANCE;
}
OperatorToObservableList() {
// singleton
}
@
Override
public
Subscriber<? super T>
call(final
Subscriber<? super
List<T>>
o) {
final
SingleDelayedProducer<
List<T>>
producer = new
SingleDelayedProducer<
List<T>>(
o);
Subscriber<T>
result = new
Subscriber<T>() {
boolean
completed;
List<T>
list = new
LinkedList<T>();
@
Override
public void
onStart() {
request(
Long.
MAX_VALUE);
}
@
Override
public void
onCompleted() {
if (!
completed) {
completed = true;
List<T>
result;
try {
/*
* Ideally this should just return Collections.unmodifiableList(list) and not copy it,
* but, it ends up being a breaking change if we make that modification.
*
* Here is an example of is being done with these lists that breaks if we make it immutable:
*
* Caused by: java.lang.UnsupportedOperationException
* at java.util.Collections$UnmodifiableList$1.set(Collections.java:1244)
* at java.util.Collections.sort(Collections.java:221)
* ...
* Caused by: rx.exceptions.OnErrorThrowable$OnNextValue: OnError while emitting onNext value: UnmodifiableList.class
* at rx.exceptions.OnErrorThrowable.addValueAsLastCause(OnErrorThrowable.java:98)
* at rx.internal.operators.OperatorMap$1.onNext(OperatorMap.java:56)
* ... 419 more
*/
result = new
ArrayList<T>(
list);
} catch (
Throwable t) {
Exceptions.
throwOrReport(
t, this);
return;
}
list = null;
producer.
setValue(
result);
}
}
@
Override
public void
onError(
Throwable e) {
o.
onError(
e);
}
@
Override
public void
onNext(T
value) {
if (!
completed) {
list.
add(
value);
}
}
};
o.
add(
result);
o.
setProducer(
producer);
return
result;
}
}