switchMap<S> method

Stream<S> switchMap<S>(Stream<S> convert(T))

Maps events to a Stream and emits values from the most recently created Stream.

When the source emits a value it will be converted to a Stream using convert and the output will switch to emitting events from that result. Like asyncExpand but the Stream emitted by a previous element will be ignored as soon as the source stream emits a new event.

This means that the source stream is not paused until a sub stream returned from the convert callback is done. Instead, the subscription to the sub stream is canceled as soon as the source stream emits a new event.

Errors from convert, the source stream, or any of the sub streams are forwarded to the result stream.

The result stream will not close until the source stream closes and the current sub stream have closed.

If the source stream is a broadcast stream, the result will be as well, regardless of the types of streams created by convert. In this case, some care should be taken:

• If convert returns a single subscription stream it may be listened to and never canceled.

See also:

• concurrentAsyncExpand, which emits events from all sub streams concurrently instead of cancelling subscriptions to previous subs streams.

Implementation

Stream<S> switchMap<S>(Stream<S> Function(T) convert) {
  return map(convert).switchLatest();
}