How to use a provider inside of another provider in Flutter

Question

I want to create an app that has an authentication service with different permissions and functions (e.g. messages) depending on the user role.

So I create

Answer 1

From version >=4.0.0, we need to do this a little differently from what @updatestage has answered.

return MultiProvider(
  providers: [
    ChangeNotifierProvider(builder: (_) => Auth()),
    ChangeNotifierProxyProvider(
      update: (context, auth, previousMessages) => Messages(auth),
      create: (BuildContext context) => Messages(null),
    ),
  ],
  child: MaterialApp(
    ...
  ),
);