add method
Adds value
to the set.
Listeners are only notified if the set changes.
Returns true
if value
(or an equal value) was not yet in the set.
Otherwise returns false
and the set is not changed
Implementation
@override
bool add(T value) {
assert(_debugAssertNotDisposed());
final result = _set!.add(value);
// Only notify if things actually changed
if (result) {
notifyListeners();
}
return result;
}