class AbstractMeta implements ChangedFlagInterface, UndoInterface, HasDatabasesInterface, VariableSpace,
  EngineMetaInterface, NamedParams, HasSlaveServersInterface, AttributesInterface, HasRepositoryInterface,
  LoggingObjectInterface {

  public void addCurrentDirectoryChangedListener( CurrentDirectoryChangedListener listener ) {
    if ( currentDirectoryChangedListeners == null ) {
      currentDirectoryChangedListeners = new ArrayList<>();
    }
    if ( listener != null && !currentDirectoryChangedListeners.contains( listener ) ) {
      currentDirectoryChangedListeners.add( listener );
    }
  }

}