toggle method
Toggles the bool value between false and true.
A shortcut for flag.value = !flag.value;
FIXME: why return this? fluent interface is not
not really a dart thing since we have '..' operator
Implementation
// ignore: avoid_returning_this
Rx<bool?>? toggle() {
if (_value != null) {
subject.add(_value = !_value!);
return this;
}
return null;
}