class AbstractMeta implements IChanged, IUndo, IVariables, IEngineMeta, INamedParams, IAttributes, ILoggingObject {

  public void addCurrentDirectoryChangedListener( ICurrentDirectoryChangedListener listener ) {
    if ( listener != null && !currentDirectoryChangedListeners.contains( listener ) ) {
      currentDirectoryChangedListeners.add( listener );
    }
  }

}