inherited_widget.dart

class MyFoo extends StatefulWidget {
  const MyFoo({Key? key, required this.child}) : super(key: key);
  final Widget child;

  @override
  MyFooState createState() => MyFooState();
  
  static MyFooState of(BuildContext context) =>
    (context.dependOnInheritedWidgetOfExactType<_MyInheritedFoo>() as _MyInheritedFoo).state;
}

class MyFooState extends State<MyFoo> {
  @override
  Widget build(BuildContext context) {
    return _MyInheritedFoo(child: widget.child, state: this);
  }
}

class _MyInheritedFoo extends InheritedWidget {
  _MyInheritedFoo({Key? key, required Widget child, required this.state}) : super(key: key, child: child);
  final MyFooState state;
  @override
  bool updateShouldNotify(covariant InheritedWidget oldWidget) => true;
}

Hey, you forgot the of method here.

Ty!