Called by an event stream when an exception is produced.
Called by an event stream when an exception is produced.
the exception passed to the observer
Called by an event stream when an event value
is produced.
Called by an event stream when an event value
is produced.
the event passed to the observer
an additional, optional value from the event source, usually null
Called by an event stream when there will be no further updates.
An object that can act upon an event or be signalled that there will be no more events.
type of events the observer responds to