StreamD

Stream that triggers the onDone event handler even when cancel() is called from a subscription. You can also add multiple onDone listeners. StreamD is a wrapper on the default Dart Stream, with an additional listenD method, but StreamD doesn't work as StreamBuilder parameter.

About StreamD

There's a minor hassle when managing Dart Streams:

• the onDone event handler is not triggered when cancel() is called from a StreamSubscription, so it may be tricky to identify the exact moment when a StreamSubscription became no longer active if we don't have access to its StreamController on a specific layer of the App.

The solution when calling listenD

• onDone event handler is always triggered once the stream is no longer active, even when cancel() is called from a StreamSubscription.

StreamD also allows you to add a listener with addOnDone that won't replace the previous onDone callback.

Comparison

final controller1 = StreamController();
final defaultStream = controller1.stream;
final defaultStreamSubscription = defaultStream.listen((event) {});
defaultStreamSubscription.onDone(() {
print("(2) Default Stream: onDone was triggered!");
});
print("(1) Default Stream: let's call cancel() on the subscription...");
defaultStreamSubscription.cancel();

final controller2 = StreamController();
final streamD = StreamD(controller2.stream);
final StreamSubscriptionD streamSubscriptionD = streamD.listenD((event) {});
streamSubscriptionD.addOnDone(() {
print("(2) With StreamD: onDone was triggered!");
});
print("(1) With StreamD: let's call cancel() on the subscription...");
streamSubscriptionD.cancel();

Output:

(1) Default Stream: let's call cancel() on the subscription...
(1) With StreamD: let's call cancel() on the subscription...
(2) With StreamD: onDone was triggered!

⚠️ Limitation

StreamD doesn't work as StreamBuilder parameter, so calling listen(..) will give you an error, please use listenD(..) instead or use the default Dart Stream.

Getting started

dependencies:
  flutter:
    sdk: flutter
        
    # Add this line:
    stream_d: ^0.3.0

Initializing a StreamD

final streamD = StreamD(stream);

Listening

final StreamSubscriptionD subscription = streamD.listenD((event) {
    print(event);
});

Adding onDone listener to a subscription

final StreamSubscriptionD subscription = streamD.listenD((event) {});
subscription.addOnDone(() {
    print("onDone was called!");
});

License

MIT

Contacting me

📧 rodrigo@wisetap.com