toBroadcastStream method

Stream<T> toBroadcastStream({ bool waitForListeners = false, bool stopWhenNoListeners = true, bool closeReceiverOnDone = false, bool sync = false, })

Convert a channel receiver to a broadcast stream for multiple listeners.

Perfect for integrating channels with Flutter widgets that expect broadcast streams, or when multiple components need to listen to the same channel data.

Parameters:

• waitForListeners: If true, doesn't start consuming until first listener
• stopWhenNoListeners: If true, pauses consumption when no listeners
• closeReceiverOnDone: If true, closes the receiver when stream ends
• sync: If true, events are delivered synchronously

Usage: {@tool snippet example/stream_to_broadcast.dart} {@end-tool}

Implementation

Stream<T> toBroadcastStream({
  bool waitForListeners = false,
  bool stopWhenNoListeners = true,
  bool closeReceiverOnDone = false,
  bool sync = false,
}) {
  final source = stream();
  StreamSubscription<T>? sub;
  late final StreamController<T> ctrl;

  final bool shouldPause = waitForListeners && stopWhenNoListeners;

  void startIfNeeded() {
    if (sub != null) return;
    sub = source.listen(
      (v) => ctrl.add(v),
      onError: ctrl.addError,
      onDone: () async {
        if (closeReceiverOnDone && !recvDisconnected) close();
        await ctrl.close();
      },
      cancelOnError: false,
    );
    if (shouldPause && !ctrl.hasListener) {
      sub!.pause();
    }
  }

  Future<void> pauseIfNeeded() async {
    final s = sub;
    if (s != null && !s.isPaused) s.pause();
  }

  Future<void> resumeIfNeeded() async {
    final s = sub;
    if (s != null && s.isPaused) s.resume();
  }

  ctrl = StreamController<T>.broadcast(
    sync: sync,
    onListen: () {
      startIfNeeded();
      if (shouldPause) resumeIfNeeded();
    },
    onCancel: () async {
      if (shouldPause && !ctrl.hasListener) {
        return pauseIfNeeded();
      }
      return;
    },
  );

  if (!waitForListeners) {
    startIfNeeded();
  }

  return ctrl.stream;
}