dispose method

@override void dispose()

Disposes this ValueListenable and sets isDisposed to true. Successive calls to this method will be ignored.

Implementation

@override
void dispose() {
  final refresh = _refresh;
  _refresh = null;
  super.dispose();
  if (refresh != null) {
    for (final listenable in _listenables) {
      listenable.removeListener(refresh);
    }
  }
}