sclass ConceptsComboBox<A extends Concept> extends JComboBox<A> {
  Concepts concepts;
  Class<A> conceptClass;
  AWTOnConceptChanges updater;
  settable bool allowNull;

  *(Concepts *concepts, Class<A> *conceptClass) {
    updateItems();
    
    updater = new AWTOnConceptChanges(concepts, this, l0 updateItems);
    updater.install();
  }
  
  void updateItems {
    var l = sortTheList(asList(freshList())
    if (allowNull) l = nullPlus(l);
    setComboBoxItems_notifyListeners(this, l));
  }
  
  swappable Cl<A> freshList() {
    ret main list(concepts, conceptClass);
  }
  
  swappable L<A> sortTheList(L<A> l) {
    ret sortConceptsByID(l);
  }
}