inherit_widget.dart

class Info extends InheritedWidget {
    // this udget uses the of(context) 
    //method to call the build method
    // when updateShouldNotify function returns true
    const Info({
      Key key,
      @required this.score,
      @required Widget child,
    }) : assert(score != null),
          assert(child != null),
          super(key: key, child: child);
    final int score;
  
    static Info of(BuildContext context) {
      return context.dependOnInheritedWidgetOfExactType<Info>();
    }
  
    @override
    bool updateShouldNotify(covariant Info oldWidget) {
      return score != oldWidget.score;
    }
  }

  // This is the widget that will call the build method
  // each time the score variable updates its value
  class CurrentScore extends StatelessWidget {
    const CurrentScore();
    @override
    Widget build(BuildContext context) {
      final Info info = Info.of(context);
  
      return Container(
        child: Text(info?.score.toString()),
      );
    }
  }

	// In this widget, we initialize the variable
  // score and send it to the inherited widget to
  // notify the child widget about the state update
  class MyWidget extends StatefulWidget {
    @override
    _MyWidgetState createState() => _MyWidgetState();
  }
  
  class _MyWidgetState extends State<MyWidget> {
  
    int _score = 0;
  
    @override
    Widget build(BuildContext context) {
      return Center(
        child: Column(
          children: [
            Info(
              score: _score,
              child:  CurrentScore(),
            ),
            ElevatedButton(
              child: const Text('Change'),
              onPressed: () {
                setState(() {
                  _score++;
                });
              },
            ),
          ],
        ),
      );
    }
  }