NavigatorState of(BuildContext context)

The state from the closest instance of this class that encloses the given context.

Typical usage is as follows:

Navigator.of(context)
  ..pop()
  ..pop()
  ..pushNamed('/settings');

Source 

static NavigatorState of(BuildContext context) {
  NavigatorState navigator = context.ancestorStateOfType(const TypeMatcher<NavigatorState>());
  assert(() {
    if (navigator == null) {
      throw new FlutterError(
        'Navigator operation requested with a context that does not include a Navigator.\n'
        'The context used to push or pop routes from the Navigator must be that of a widget that is a descendant of a Navigator widget.'
      );
    }
    return true;
  });
  return navigator;
}