Bloc: Cannot access state after migration to 6.0.1

[YanaKrivitskaya]

I've migrated my app to flutter_bloc: ^6.0.1 and now I'm getting exception The getter '...' was called on null. when trying to access state property.

To Reproduce
Once app is loaded it redirects user to LoginSignupPage. Here is the code of the page:

class LoginSignupPage extends StatelessWidget{
  final UserRepository _userRepository;

  LoginSignupPage({@required UserRepository userRepository})
    :assert (userRepository != null),
    _userRepository = userRepository;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: BlocProvider<LoginSignupBloc>(
        create: (context) => LoginSignupBloc(userRepository: _userRepository),
        child: LoginSignupForm(userRepository: _userRepository),
      ),
    );
  }
}

Then on LoginSignupForm I'm trying to show either Login or Register form depending on state parameter:

class LoginSignupForm extends StatefulWidget{
  final UserRepository _userRepository;

  LoginSignupForm({@required UserRepository userRepository})
    :assert (userRepository != null),
        _userRepository = userRepository;

  State<LoginSignupForm> createState() => _LoginSignupFormState();
}

class _LoginSignupFormState extends State<LoginSignupForm>{

  LoginSignupBloc _loginSignupBloc;

  UserRepository get _userRepository => widget._userRepository;

  @override
  void initState() {
    super.initState();
    _loginSignupBloc = BlocProvider.of<LoginSignupBloc>(context);    
  }

  @override
  Widget build(BuildContext context) {
    return BlocListener<LoginSignupBloc, LoginSignupState>(
      listener: (context, state){ 
        if(state.isLoginForm){
          this.linkText = "Don't have an account?";
          this.linkButtonText = "Create new";
          this.actionText = "Login";
        }
        if(state.isRegisterForm){
          this.linkText = "Already have an account?";
          this.linkButtonText = "Login";
          this.actionText = "Register";
        }    
      },
      child: BlocBuilder<LoginSignupBloc, LoginSignupState>(
        builder: (context, state){
          return Center(
            child: SingleChildScrollView(
              child: Container(                
                child: Column(
                  children: <Widget>[
                    _header(),
                    Container(
                      margin: const EdgeInsets.only(top: 40, left: 20, right: 20, bottom: 20),
                      child: Builder(
                        builder: (context) => Form(
                          key: _formKey,
                          child: Column(
                            children: <Widget>[                              
                              state.isRegisterForm ? _usernameTextField(_usernameController, state) : Container(height: 0, width: 0,),
                              !state.isPasswordReseted ?  _emailTextField(_emailController, state) : Container(height: 0, width: 0,),
                              _passwordResetInfo(state),
                              state.isLoginForm || state.isRegisterForm ? _passwordTextField(_passwordController, state) : Container(height: 0, width: 0,),
                              state.isLoginForm ? _forgotPasswordLink() : Container(height: 0, width: 0,),
                              _showErrorMessage(),
                              _progressIndicator(),
                              !state.isPasswordReseted ? _submitButton(state) : Container(height: 0, width: 0,),
                              _footerLink(state)
                            ], ), ),),)],),),));}),);}...}

I'm getting error on widget child: Builder :
The getter 'isRegisterForm' was called on null.
Receiver: null
Tried calling: isRegisterForm

Expected behavior
Worked fine on bloc version 4.0.0

[felangel]

Hi @YanaKrivitskaya 👍
Thanks for opening an issue!

I'm guessing this is because you didn't update the bloc to pass the initial state to super

LoginSignupBloc() : super(LoginSignupState());

Previously, you would provide the initial state via the initialState getter like:

@override
LoginSignupState get initialState => LoginSignupState();

but the initialState override has been removed and you must now provide the initial state to super. Let me know if that helps 👍

[YanaKrivitskaya]

@felangel This is how my LoginSignupBloc looks like:

class LoginSignupBloc extends Bloc<LoginSignupEvent, LoginSignupState> {
  UserRepository _userRepository;

  LoginSignupBloc({@required UserRepository userRepository}) : assert (userRepository != null),
      _userRepository = userRepository, super(LoginSignupState.empty());

... }

And this is how it was initialized previously:

@override
  LoginSignupState get initialState => LoginSignupState.empty();

So I've added super(LoginSignupState.empty()) but the error persists.

[felangel]

@YanaKrivitskaya are you able to share a link to the project? If not can you provide the complete bloc and state implementations?

[YanaKrivitskaya]

@felangel Here is the whole LoginSignup component
https://github.com/YanaKrivitskaya/traces/tree/TRC-52-visa---show-existing-visas-functi/traces/lib/loginSignup

[felangel]

I just took a look and cloned the project and was not able to reproduce the issue 🤔
What steps should I take to reproduce the error?

[YanaKrivitskaya]

@felangel Strange. I'm getting error right after app loads. Let me try to reinstall it...

Were you using code from branch TRC-52-...?

[felangel]

sounds good 👍
yup, I checked out the same branch and everything worked. If you're still seeing the error message me on discord and we can debug it live 😄

[YanaKrivitskaya]

@felangel Magic thing but it works fine after reinstallation 😃
Thanks for your prompt response and advise!

[felangel]

Awesome, glad to hear it 😄