stream_d 0.0.2

Stream that triggers the onDone event handler even when cancel() is called from a subscription. You can also add multiple onDone listeners and close all subscriptions from the stream. StreamD is based [...]

StreamD

Stream that triggers the onDone event handler even when cancel() is called from a subscription. You can also add multiple onDone listeners and close all subscriptions from the stream. StreamD is based on the default Dart Stream.

About StreamD

The problem with default streams:

• the default 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is called from a StreamSubscription, so it may be tricky to identify the exact moment when a StreamSubscription became no longer active if we don't have access to its StreamController on a specific layer of the App.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• onDone event handler is always triggered once the stream is no longer active, even when cancel() is called from a StreamSubscription.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 and you can also close all StreamSubscription by calling closeAll`

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

Getting started

dependencies:
  flutter:
    sdk: flutter
        
    # Add this line:
    stream_d: ^0.0.1

Initializing a StreamD

You can either initialize a Stream from a controller in case you have access to it, or from a Stream (e.g. from Firebase)

Initializing StreamD from a controller

final controller = StreamController();
final streamD = StreamD(controller: controller);

Initializing StreamD from a stream

final stream = firestore.collection("messages").doc(conversationId).snapshots();
final streamD = StreamD.fromStream(stream);

Usage

Listening

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

Adding onDone listener to a subscription

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

In case you want to close all subscriptions

streamD.close();

Avoid calling listen and onDone from StreamD

It's important to call these methods when using StreamD:

• call listenD, not listen
• call addOnDone, not onDone

listen and onDone are available for StreamBuilder internal usage only, so if you want to still use them, please use the default Stream instead.

License

MIT

Contacting me

📧 [e-mail]