on<E extends Event> method

void on<E extends Event>(_HandlerFn<E, State> fn)

Register an event handler for an event of type E. There should only ever be one event handler per event type E.

Implementation

void on<E extends Event>(
  _HandlerFn<E, State> fn,
) {
  final registered = _handlers.any((handler) => handler.type == E);
  assert(
    !registered,
    'on<$E> was called multiple times.', // coverage:ignore-line
  );
  _handlers.add(
    _Handler(
      isType: (e) => e is E,
      type: E,
      fn: fn,
    ),
  );
}