[question] example to access API backend using form_block 0.12.0

[hansbak]

Can somebody give me an example how to access a backend API using the latest 0.12.0 version of form_bloc? It needs already be defined in main.dart...and then implemented in the bloc I have it working in the bloc, but want it already started in main.dart so it does not restart with every screen. Thanks in advance! Hans

[GiancarloCode]

Hello The way I recommend is to inject your service / repository using the constructor, then you can use it whatever you want.

  MyFormBloc({
    @required Repository repository,
  })  : _repository = repository,
     {
    addFieldBlocs(
      fieldBlocs: [field1, field2, fieldN],
    );
  } 
  final Repository _repository;

  @override
  void onSubmitting() async {
    try {
      await _repository.awesomeMethod(
        field1.value,
        field2.value,
      );
      emitSuccess();
    } catch (e) {
      emitFailure();
    }
  }

If you need to fill the fields with data from backend, check this tutorial

Maybe you want to serialize the form, check out this tutorial

---

The recommended architecture is the same one that bloc library recommend. https://bloclibrary.dev/#/architecture

---

Do you have any doubt?

[hansbak]

woow thanks for the quick response!

[hansbak]

OK, i tried to implement https://bloclibrary.dev/#/architecture, the login example with your suggestion of the myFormBloc above. I am stuck how to implement this in the LoginForm which has two extends, in the https://bloclibrary.dev/#/architecture example there is just one.

In the LoginForm I have now the userRepository undefined in:

return BlocProvider(
  create: (context) => LoginFormBloc(
        authenticationBloc: BlocProvider.of<AuthenticationBloc>(context),
        userRepository: userRepository,
  ),

Would be nice to have an example combining your form_bloc and the login example in https://bloclibrary.dev/#/architecture?

regards, Hans

[GiancarloCode]

Hello Has two extends and the example just one? I did not understand :(, can you explain better? I'll add an example these days :),

[hansbak]

in your LoginForm:

class LoginForm extends StatefulWidget { @override _LoginFormState createState() => _LoginFormState(); } class _LoginFormState extends State { LoginFormBloc _formBloc; List _focusNodes;

in the https://bloclibrary.dev/#/architecture:

class LoginPage extends StatelessWidget { final UserRepository userRepository;

LoginPage({Key key, @required this.userRepository}) : assert(userRepository != null), super(key: key);

@override Widget build(BuildContext context) {

if you can write the example I am sure more people than me would find this very useful..... thanks for the fantastic form_bloc and your site at: https://giancarlocode.github.io/form_bloc/#/ probably all written in flutter is awsome!

[GiancarloCode]

Thank you, Although as I see, your confusion it's more about the stateful widgets and stateless widgets Check out this official flutter tutorial https://flutter.dev/docs/development/ui/interactive#stateful-and-stateless-widgets

I would also like you to tell me more specifically what you want to see in the example :)

I stay tuned :)

[hansbak]

Hi Gian,

what is needed here is your 'simple' example at https://giancarlocode.github.io/form_bloc/#/ extended with userRepository and Authentication bloc/states/events from https://bloclibrary.dev/#/flutterlogintutorial

thank you in advance for your help!

[hansbak]

Hi Gian, i think i done it, have a look at: https://github.com/hansbak/flutter_form_bloc_userRepository

let me know your comments!

regards, Hans

[GiancarloCode]

Yes, that's pretty good.

But in this part use a try / catch with the repository method.

  @override
  void onSubmitting() async {
    try{
      final token = await userRepository.authenticate(
        username: email.value,
        password: password.value,
      );
      authenticationBloc.add(LoggedIn(token: token));
    } catch (e) {
       // TODO: Map exception to error message 
       emitFailure(failureResponse: e.toString());
    }
  }

The other week I will upload a complete project and you can review, but you already have the general idea :)

[hansbak]

Thanks for your comment!

Will review your version!

[eugene123tw]

I was also trying to figure out how to pass Authentication repository to form BLoC and this helped me a lot!