How to have single instance of a bloc across other blocs - flutter

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