CODEWITHSUNDEEP
flutterdartstream
sn0ep
sn0ep

Reputation: 3943

create future out of stream when stream yields certain value

I have a stream that yields CallEvent objects. I want to call this stream but I'm interested in one particular event and want to consume it as a future. Is this possible?

Pseudo code of what I'm trying to achieve:

final Stream<CallEvent> aStreamOfEvents = repo.getEvents();

// However of this stream im only interested in the `ResponseEvent`

final Future<ResponseEvent> response = 
       aStreamOfEvents.filter((event) { event is ResponseEvent}).toFuture()

Is this possible and if yes how?

Upvotes: 1

Views: 145

Answers (1)

Nate Bosch
Nate Bosch

Reputation: 10935

final response = aStreamOfEvents.firstWhere((e) => e is ResponseEvent);

response is a Future<CallEvent> above, so if you need a Future<ResponseEvent> you'd need something like:

final response = aStreamOfEvent
    .firstWhere((e) => e is ResponseEvent)
    .then((e) => e as ResponseEvent);

Or, alternatively, if you use package:stream_transform.

final response = aStreamOfEvent
    .transform(whereType<ResponseEvent>())
    .first

If the Stream closes without emitting a ResponseEvent then the future will complete with an error in all of these cases. The specific error will depend on which pattern you chose.

Upvotes: 3

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