updater method
      
void
updater(
    
    
- T newValue
Implementation
void updater(T newValue) {
  if (widget.onUpdate != null) {
    widget.onUpdate!(newValue);
  }
  setState(() {
    value = newValue;
  });
}void updater(T newValue) {
  if (widget.onUpdate != null) {
    widget.onUpdate!(newValue);
  }
  setState(() {
    value = newValue;
  });
}