How to set data in an inherited widget from a another widget?

Question

So inherited widget is useful for passing data down the tree, but how do I set that data in the first place if inherited widgets are immutable? I'm trying to set a phone number for OTP auth and then display that number on another screen. Provider is kind of advanced for me at the moment, how do I approach this? thank you

Answer 1

You have to rebuild somewhere your InheritedWidget. You can use any stage management for it, for example you can use StatefulWidget:

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

class MyInheritedWidget extends InheritedWidget {
 final int counter;

 MyInheritedWidget({Key key, this.counter, Widget child})
     : super(key: key, child: child);

 @override
 bool updateShouldNotify(MyInheritedWidget oldWidget) {
   return oldWidget.counter != counter;
 }

 static MyInheritedWidget of(BuildContext context) {
   return context.dependOnInheritedWidgetOfExactType<MyInheritedWidget>();
 }
}

void main() {
 runApp(MyApp());
}

class MyApp extends StatelessWidget {
 @override
 Widget build(BuildContext context) {
   return MaterialApp(
     home: Home(),
   );
 }
}

class Home extends StatefulWidget {
 @override
 _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
 int _counter = 0;

 @override
 Widget build(BuildContext context) {
   return Scaffold(
     body: Center(
       child: MyInheritedWidget(counter: _counter, child: CounterWidget()),
     ),
     floatingActionButton: FloatingActionButton(
       onPressed: () {
         setState(() {
           _counter++;
         });
       },
     ),
   );
 }
}

class CounterWidget extends StatelessWidget {
 @override
 Widget build(BuildContext context) {
   return Text("${MyInheritedWidget.of(context).counter}",
       style: TextStyle(fontSize: 100));
 }
}

Answer 2

Firstly you would use a StreamProvider for your stream of data (The same as you would using a StreamBuilder):

class Widget1 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return StreamProvider<User>.value(
      value: AuthService().user,
      child: Wrapper(),
    );
  }
}

Next widget has no required data

class Widget2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      child: Widget3(),
    );
  }
}

Access your data via Provider.of

class Widget3 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final user = Provider.of<User>(context);
    if (user == null) {
      return Login();
    } else {
      return Dashboard();
    }
  }
}

With this method, you still need to access the data somewhere down the widget tree. You can't go up, if you want to have the ability to have a widget up the tree listen to something that happens down the tree, you will want to look at ChangeNotifier