InheritedWidget override

inherited_widget_override_example.dart

import 'package:flutter/material.dart';

class Service {
  final String authToken;
  Service({this.authToken});

  getData() async {
    if (authToken == null) {
      fetchAnonymous();
    } else {
      fetchAuthenticated(authToken);
    }
  }
}

class ServiceProvider extends InheritedWidget {
  final Widget child;
  final String authToken;

  Service get service => Service(authToken: authToken);

  ServiceProvider({Key key, this.child, this.authToken})
      : super(key: key, child: child);

  @override
  bool updateShouldNotify(ServiceProvider oldWidget) {
    return oldWidget.child != child || oldWidget.authToken != authToken;
  }

  static ServiceProvider of(BuildContext context) =>
      context.dependOnInheritedWidgetOfExactType<ServiceProvider>();
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ServiceProvider(
      // no auth token, anonymous flow
      child: MaterialApp(
        home: Anonymous(),
      ),
    );
  }
}

class Anonymous extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final service = ServiceProvider.of(context).service;

    // service is anonymous here

    return Container(
      // override anonymous service from MyApp and make everything below this widget authenticated
      child: ServiceProvider(
        authToken: 'Bearer 1234',
        child: AuthenticatedWidget(),
      ),
    );
  }
}