off method
Implementation
void off(String event, [EventHandler? handler]) {
if (handler != null) {
_events[event]?.remove(handler);
_eventsOnce[event]?.remove(handler);
if (_events[event]?.isEmpty == true) {
_events.remove(event);
}
if (_eventsOnce[event]?.isEmpty == true) {
_eventsOnce.remove(event);
}
} else {
_events.remove(event);
_eventsOnce.remove(event);
}
}