# drain<E> method

Future<E> drain <E>([E futureValue ])

Discards all data on the stream, but signals when it's done or an error occurred.

When subscribing using drain, cancelOnError will be true. This means that the future will complete with the first error on the stream and then cancel the subscription.

In case of a `done` event the future completes with the given `futureValue`.

## Implementation

    Future<E> drain<E>([E futureValue]) =>
        listen(null, cancelOnError: true).asFuture<E>(futureValue);