How to throttle events in bloc?

Question

How to throttle events in bloc? Let's say, I want to trigger file save on user input, but perform file system access not more often than once per 100ms?

Example bloc event handler:

on<StoreFile>(_handleStoreEvent);

Answer 1

Each handler have an optional transformer: field which can do throttling (and much more).

Using rxdart you can implement throttling yourself:

on<StoreFile>(
  _handleStoreEvent,
  transformer: (events, mapper) => events.throttleTime(Duration(milliseconds: 100)).switchMap(mapper),
);

I wrote the bloc_event_transformers package to do popular transforms like throttle and debounce to reduce the boilerplate in my apps. It can be used like that:

on<StoreFile>(
  _handleStoreEvent,
  transformer: throttle(Duration(milliseconds: 100)),
);