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
onDoneevent handler is not triggered whencancel()is called from aStreamSubscription, so it may be tricky to identify the exact moment when aStreamSubscriptionbecame no longer active if we don't have access to itsStreamControlleron a specific layer of the App.
The solution when calling listenD
onDoneevent handler is always triggered once the stream is no longer active, even whencancel()is called from aStreamSubscription.
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!
:warning: 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!");
});