asFuture<E> method
Returns a future that handles the onDone and onError callbacks.
This method overwrites the existing onDone and onError callbacks with new ones that complete the returned future.
In case of an error the subscription will automatically cancel (even
when it was listening with cancelOnError set to false).
In case of a done event the future completes with the given
futureValue.
If futureValue is omitted, the value null as E is used as a default.
If E is not nullable, this will throw immediately when asFuture
is called.
Implementation
@override
Future<E> asFuture<E>([E? futureValue]) => Future.value(futureValue);