on<T, P> method
Puts on to listen eventName
event.
When the event is emitted(by emit), the callback
is called.
Implementation
void on<T, P>(
Object? instance,
Enum eventName,
CallbackEvent<T, P> callback,
) {
var notifier = ReactterNotifier(instance, eventName);
notifier = _notifiers.lookup(notifier) ?? notifier;
notifier.addListener(callback);
_notifiers.add(notifier);
}