form_bloc #

Easy Form State Management using BLoC pattern. Separate the Form State and Business Logic from the User Interface. Async Validation, Progress, Failures, Successes, and more.

To create beautiful forms in Flutter using form_bloc check out flutter_form_bloc.

Before to use this package you need to know the core concepts of bloc package.

Examples #

• FieldBlocs with async validation: BLoC - UI.
• Manually set FieldBloc error: BLoC - UI.
• FormBloc with submission progress: BLoC - UI.
• FormBloc without auto validation: BLoC - UI.
• Complex async prefilled FormBloc: BLoC - UI.
• And more examples.

Basic Example #

dependencies:
  form_bloc: ^0.6.0

import 'package:form_bloc/form_bloc.dart';

class LoginFormBloc extends FormBloc<String, String> {
  final emailField = TextFieldBloc(validators: [Validators.email]);
  final passwordField = TextFieldBloc();

  final UserRepository _userRepository;

  LoginFormBloc(this._userRepository);

  @override
  List<FieldBloc> get fieldBlocs => [emailField, passwordField];

  @override
  Stream<FormBlocState<String, String>> onSubmitting() async* {
    try {
      _userRepository.login(
        email: emailField.value,
        password: passwordField.value,
      );
      yield state.toSuccess();
    } catch (e) {
      yield state.toFailure();
    }
  }
}

Basic use #

1. Import it #

import 'package:form_bloc/form_bloc.dart';

2. Create a class that extends FormBloc<SuccessResponse, FailureResponse>

FormBloc<SuccessResponse, FailureResponse>

SuccessResponse The type of the success response.

FailureResponse The type of the failure response.

For example, the SuccessResponse type and FailureResponse type of LoginFormBloc will be String

import 'package:form_bloc/form_bloc.dart';

class LoginFormBloc extends FormBloc<String, String> {}

2. Create Field Blocs #

You need to create field blocs, and these need to be final.

You can create:

• InputFieldBloc<Value>.
• TextFieldBloc.
• BooleanFieldBloc.
• SelectFieldBloc<Value>.
• MultiSelectFieldBloc<Value>.

For example the LoginFormBloc will have two TextFieldBloc.

import 'package:form_bloc/form_bloc.dart';

class LoginFormBloc extends FormBloc<String, String> {
  final emailField = TextFieldBloc(validators: [Validators.email]);
  final passwordField = TextFieldBloc();
}

3. Add Services/Repositories #

In this example we need a UserRepository for make the login.

import 'package:form_bloc/form_bloc.dart';

class LoginFormBloc extends FormBloc<String, String> {
  final emailField = TextFieldBloc(validators: [Validators.email]);
  final passwordField = TextFieldBloc();

  final UserRepository _userRepository;

  LoginFormBloc(this._userRepository);
}

4. Implement the get method fieldBlocs #

You need to override the get method fieldBlocs and return a list with all FieldBlocs.

For example the LoginFormBloc need to return a List with emailField and passwordField.

import 'package:form_bloc/form_bloc.dart';

class LoginFormBloc extends FormBloc<String, String> {
  final emailField = TextFieldBloc(validators: [Validators.email]);
  final passwordField = TextFieldBloc();

  final UserRepository _userRepository;

  LoginFormBloc(this._userRepository);

  @override
  List<FieldBloc> get fieldBlocs => [emailField, passwordField];
}

5. Implement onSubmitting method #

onSubmitting returns a Stream<FormBlocState<SuccessResponse, FailureResponse>>.

This method is called when you call loginFormBloc.submit() and FormBlocState.isValid is true, so each field bloc has a valid value.

You can get the current value of each field bloc calling emailField.value or passwordField.value.

You must call all your business logic of this form here, and yield the corresponding state.

You can yield a new state using:

• state.toFailure([FailureResponse failureResponse]).
• state.toSuccess([SuccessResponse successResponse]).
• state.toLoaded().

See other states here.

For example onSubmitting of LoginFormBloc will return a Stream<FormBlocState<String, String>> and yield state.toSuccess() if the _userRepository.login method not throw any exception, and yield state.toFailure() if throw a exception.

import 'package:form_bloc/form_bloc.dart';

class LoginFormBloc extends FormBloc<String, String> {
  final emailField = TextFieldBloc(validators: [Validators.email]);
  final passwordField = TextFieldBloc();

  final UserRepository _userRepository;

  LoginFormBloc(this._userRepository);

  @override
  List<FieldBloc> get fieldBlocs => [emailField, passwordField];

  @override
  Stream<FormBlocState<String, String>> onSubmitting() async* {
    try {
      _userRepository.login(
        email: emailField.value,
        password: passwordField.value,
      );
      yield state.toSuccess();
    } catch (e) {
      yield state.toFailure();
    }
  }
}

Credits #

This package uses the following packages:

• bloc
• rxdart
• equatable
• quiver