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

  *(Concepts *concepts, Class<A> *conceptClass) {
    updateItems();
    
    updater = new AWTOnConceptChanges(concepts, this, l0 updateItems);
    updater.install();
  }
  
  void updateItems {
    var l = sortTheList(filterTheList(freshList()));
    if (allowNull) l = nullPlus(l);
    setComboBoxItems_notifyListeners(this, l);
  }
  
  swappable Cl<A> freshList() {
    ret filterTheList( main list(concepts, conceptClass);
  }
  
  L<A> filterTheList(Cl<A> l) {
    ret filter == null ? asList(l) : filter(filter, l);
  }
  
  swappable L<A> sortTheList(L<A> l) {
    ret sortConceptsByID(l);
  }
  
  A get() { ret getSelectedItem_typed(this); }
  
  void select(long conceptID) {
    main setSelectedItem(this, getConcept(concepts, conceptClass, conceptID));
  }
}