LibTest/async/Stream/asBroadcastStream_A01_t05.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.

// @dart = 2.9

/// @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 returned stream will subscribe to this stream
/// when its first subscriber is added.
/// @author a.semenov@unipro.ru

import "dart:async";
import "../../../Utils/expect.dart";

main() {
  bool hasListener = false;
  StreamController controller = new StreamController(
      onListen:(){ hasListener = true;}
  );
  Stream b = controller.stream.asBroadcastStream();
  Expect.isFalse(hasListener);
  asyncMultiStart(2);
  b.listen(
    (_) {
      Expect.isTrue(hasListener);
      asyncEnd();
    }
  );
  b.listen(
    (_) {
      Expect.isTrue(hasListener);
      asyncEnd();
    }
  );
  Expect.isTrue(hasListener);
  controller.add("a");
  new Future(() => controller.close());
}