LibTest/async/Stream/asBroadcastStream_A01_t06.dart

// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

/**
 * @assertion Stream<T> asBroadcastStream (
 *   {void onListen(StreamSubscription<T> subscription),
 *    void onCancel(StreamSubscription<T> subscription)})
 * Returns a multi-subscription stream that produces the same events as this.
 *
 * The returned stream will subscribe to this stream when its first subscriber
 * is added, and will stay subscribed until this stream ends, or a callback
 * cancels the subscription.
 *
 * @description Checks that the returned stream will unsubscribe from
 * this stream when onListen callback cancels the subscription.
 *
 * @author a.semenov@unipro.ru
 */
import "dart:async";
import "../../../Utils/expect.dart";

main() {
  bool hasListener = false;
  bool listenerCancelled = false;
  StreamController controller = new StreamController(
      onListen:() { hasListener = true;},
      onCancel:() { listenerCancelled = true;}
  );
  Stream b = controller.stream.asBroadcastStream(
    onListen:(StreamSubscription subscription){
      subscription.cancel();
    }
  );
  Expect.isFalse(hasListener);
  Expect.isFalse(listenerCancelled);

  b.listen(null);
  Expect.isTrue(hasListener);
  Expect.isTrue(listenerCancelled);
  controller.add("a");
  controller.add("b");
  controller.close();
}