How to have single instance of a bloc across other blocs

Question

How can I avoid creating another instance of some bloc class? I have two blocs: LoginBloc and AuthBloc . and LoginBloc accepts an instance of AuthBLoc and here is problem:

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

class MyApp extends StatelessWidget {

  final UserRepository repository=UserRepository();

  @override
  Widget build(BuildContext context) {
    return MultiBlocProvider(
        providers: [
          BlocProvider(
            create: (context) => LoginBloc(
              //******Extra Instance of AuthBloc in being created here because LoginBloc needs it to listen********
              authBloc: AuthBloc(SInitialState(),userRepository: repository), userRepository:repository
            ),
          ),
          BlocProvider(
            create: (context) => AuthBloc(SInitialState(),userRepository: repository),
          )
        ],
        child: MaterialApp(...);

Thanks in advance.

Answer 1

You can assign AuthBloc to a variable inside build() method.

Or, just nest one BlockProvider inside another one:

  BlocProvider<AuthBloc>(
    create: (context) => AuthBloc(SInitialState(),userRepository: repository),
    child: BlocBuilder<AuthBloc, AuthState>(
      builder: (BuildContext context, AuthState authState) { 
        return BlocProvider(
          create: (context) => LoginBloc(
              authBloc: context.bloc<AuthBloc>(), 
              userRepository: repository,
            ),
          child: MaterialApp(...),
          )
        })
      ),

But the best solution is Bloc to Bloc communication

Answer 2

if I got you question correctly, you might use GetIt and here is a sample code

MultiBlocProvider(
      providers: [
        BlocProvider<SginInBloc>(
          create: (BuildContext context) => sl<SginInBloc>(),
          child: SginInPage(),
        ),....

so that you will get access to the instans of that Bloc that will be created

 final sl = GetIt.instance;
  sl.registerFactory(() => SginInBloc();

here I'm using registerFactory but you can use registerSingleton depends on what you want to achive

Answer 3

void main() {
  final UserRepository repository=UserRepository();
  runApp(MyApp(authBloc: AuthBloc(),userRepo : repository));
}

class MyApp extends StatelessWidget {
  final AuthBloc authBloc;
  final UserRepository userRepo;
  MyApp({required this.authBloc,required this.userRepo});


  @override
  Widget build(BuildContext context) {
    return MultiBlocProvider(
        providers: [
          BlocProvider(
            create: (context) => LoginBloc(
              //******Extra Instance of AuthBloc in being created here because LoginBloc needs it to listen********
              authBloc: authBloc,userRepository: userRepo), userRepository:userRepo
            ),
          ),
          BlocProvider(
            create: (context) => authBloc,
          )
        ],
        child: MaterialApp(...);

Try this