| // Copyright 2014 Google Inc. All Rights Reserved. |
| // |
| // 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. |
| |
| part of quiver.async; |
| |
| /** |
| * A Stream that will emit the same values as the stream returned by [future] |
| * once [future] completes. |
| * |
| * If [future] completes to an error, the return value will emit that error and |
| * then close. |
| * |
| * If [broadcast] is true, this will be a broadcast stream. This assumes that |
| * the stream returned by [future] will be a broadcast stream as well. |
| * [broadcast] defaults to false. |
| * |
| * # Example |
| * |
| * This class is useful when you need to retreive some object via a `Future`, |
| * then return a `Stream` from that object: |
| * |
| * var futureOfStream = getResource().then((resource) => resource.stream); |
| * return new FutureStream(futureOfStream); |
| */ |
| class FutureStream<T> extends Stream<T> { |
| Future<Stream<T>> _future; |
| StreamController<T> _controller; |
| StreamSubscription _subscription; |
| |
| FutureStream(Future<Stream<T>> future, {bool broadcast: false}) { |
| _future = future.catchError((e, stackTrace) { |
| // Since [controller] is synchronous, it's likely that emitting an error |
| // will cause it to be cancelled before we call close. |
| if (_controller != null) { |
| _controller.addError(e, stackTrace); |
| _controller.close(); |
| } |
| _controller = null; |
| }); |
| |
| if (broadcast == true) { |
| _controller = new StreamController.broadcast( |
| sync: true, onListen: _onListen, onCancel: _onCancel); |
| } else { |
| _controller = new StreamController( |
| sync: true, onListen: _onListen, onCancel: _onCancel); |
| } |
| } |
| |
| _onListen() { |
| _future.then((stream) { |
| if (_controller == null) return; |
| _subscription = stream.listen(_controller.add, |
| onError: _controller.addError, onDone: _controller.close); |
| }); |
| } |
| |
| _onCancel() { |
| if (_subscription != null) _subscription.cancel(); |
| _subscription = null; |
| _controller = null; |
| } |
| |
| StreamSubscription<T> listen(void onData(T event), |
| {Function onError, void onDone(), bool cancelOnError}) { |
| return _controller.stream.listen(onData, |
| onError: onError, onDone: onDone, cancelOnError: cancelOnError); |
| } |
| |
| bool get isBroadcast => _controller.stream.isBroadcast; |
| } |