flutter_form_bloc 0.10.3

Create Beautiful Forms in Flutter. The easiest way to Prefill, Async Validation, Update Form Fields, and Show Progress, Failures or Navigate by Reacting to the Form State.

flutter_form_bloc

Create Beautiful Forms in Flutter. The easiest way to Prefill, Async Validation, Update Form Fields, and Show Progress, Failures, Successes or Navigate by Reacting to the Form State.

Separate the Form State and Business Logic from the User Interface using form_bloc.

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To see complex examples, check out the example project.

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Before to use this package you need to know the core concepts of bloc package and the basics of flutter_bloc

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Widgets

• TextFieldBlocBuilder: A material design text field that can show suggestions.
• DropdownFieldBlocBuilder: A material design dropdown.
• RadioButtonGroupFieldBlocBuilder: A material design radio buttons.
• CheckboxFieldBlocBuilder: A material design checkbox.
• SwitchFieldBlocBuilder: A material design switch.
• CheckboxGroupFieldBlocBuilder: A material design checkboxes.
• FormBlocListener: BlocListener that reacts to the state changes of the FormBloc.

Note

FormBloc, InputFieldBloc, TextFieldBloc, BooleanFieldBloc, SelectFieldBloc, MultiSelectFieldBloc are blocs, so you can use BlocBuilder or BlocListener of flutter_bloc for make any widget you want compatible with any FieldBloc or FormBloc.

If you want me to add other widgets please let me know, or make a pull request.

Examples

• Form with dynamic fields: BLoC - UI.
• 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: ^0.10.0
  flutter_form_bloc: ^0.10.0

import 'package:form_bloc/form_bloc.dart';

class LoginFormBloc extends FormBloc<String, String> {
  LoginFormBloc() {
    addFieldBloc(
      fieldBloc: TextFieldBloc(
        name: 'email',
        validators: [FieldBlocValidators.email],
      ),
    );

    addFieldBloc(
      fieldBloc: TextFieldBloc(
        name: 'password',
        validators: [FieldBlocValidators.requiredTextFieldBloc],
      ),
    );
  }

  @override
  Stream<FormBlocState<String, String>> onSubmitting() async* {
    // Login logic...

    // Get the fields values:
    print(state.fieldBlocFromPath('email').asTextFieldBloc.value);
    print(state.fieldBlocFromPath('password').asTextFieldBloc.value);

    await Future<void>.delayed(Duration(seconds: 2));
    yield state.toSuccess();
  }
}

import 'package:flutter/material.dart';
import 'package:flutter_form_bloc/flutter_form_bloc.dart';
import 'package:flutter_form_bloc_example/widgets/widgets.dart';
import 'package:flutter_form_bloc_example/forms/login_form_bloc.dart';

class LoginForm extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return BlocProvider<LoginFormBloc>(
      create: (context) => LoginFormBloc(),
      child: Builder(
        builder: (context) {
          return Scaffold(
            appBar: AppBar(title: Text('Simple login')),
            body: FormBlocListener<LoginFormBloc, String, String>(
              onSubmitting: (context, state) => LoadingDialog.show(context),
              onSuccess: (context, state) {
                LoadingDialog.hide(context);
                Navigator.of(context).pushReplacementNamed('success');
              },
              onFailure: (context, state) {
                LoadingDialog.hide(context);
                Notifications.showSnackBarWithError(
                    context, state.failureResponse);
              },
              child: BlocBuilder<LoginFormBloc, FormBlocState>(
                builder: (context, state) {
                  return ListView(
                    physics: ClampingScrollPhysics(),
                    children: <Widget>[
                      TextFieldBlocBuilder(
                        textFieldBloc: state.fieldBlocFromPath('email'),
                        keyboardType: TextInputType.emailAddress,
                        decoration: InputDecoration(
                          labelText: 'Email',
                          prefixIcon: Icon(Icons.email),
                        ),
                      ),
                      TextFieldBlocBuilder(
                        textFieldBloc: state.fieldBlocFromPath('password'),
                        suffixButton: SuffixButton.obscureText,
                        decoration: InputDecoration(
                          labelText: 'Password',
                          prefixIcon: Icon(Icons.lock),
                        ),
                      ),
                      FormButton(
                        text: 'LOGIN',
                        onPressed: context.bloc<LoginFormBloc>().submit,
                      ),
                    ],
                  );
                },
              ),
            ),
          );
        },
      ),
    );
  }
}

Basic usage

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> {}

3. Create the Field Blocs

Add the field blocs to the form bloc using addFieldBloc method.

You can create:

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

For example the LoginFormBloc will have two TextFieldBloc.

The name parameter must be an unique string and will serve to identify that field bloc.

The state of the form has a Map<String, FieldBloc> fieldBlocs property, in which each field bloc can be accessed using its name as a key.

import 'package:form_bloc/form_bloc.dart';

class LoginFormBloc extends FormBloc<String, String> {
  LoginFormBloc() {
    addFieldBloc(
      fieldBloc: TextFieldBloc(
        name: 'email',
        validators: [FieldBlocValidators.email],
      ),
    );

    addFieldBloc(
      fieldBloc: TextFieldBloc(
        name: 'password',
        validators: [FieldBlocValidators.requiredTextFieldBloc],
      ),
    );
  }
}

4. 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.

To get the value of each field bloc you can do it through the state of the form bloc, and using the fieldBlocFromPath method that receives a path and will return the corresponding field bloc. Then you will have to cast the corresponding type and you will get the value by using the value property.

The path is a String that allows easy access to the Map<String, FieldBloc> fieldBlocs that is found in state.fieldBlocs.

To access nested field Blocs, you must use the / character.

Examples:

• email
• group1/name
• group1/group2/name/

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.

import 'package:form_bloc/form_bloc.dart';

class LoginFormBloc extends FormBloc<String, String> {
  LoginFormBloc() {
    addFieldBloc(
      fieldBloc: TextFieldBloc(
        name: 'email',
        validators: [FieldBlocValidators.email],
      ),
    );

    addFieldBloc(
      fieldBloc: TextFieldBloc(
        name: 'password',
        validators: [FieldBlocValidators.requiredTextFieldBloc],
      ),
    );
  }

  @override
  Stream<FormBlocState<String, String>> onSubmitting() async* {
    // Login logic...

    // Get the fields values:
    print(state.fieldBlocFromPath('email').asTextFieldBloc.value);
    print(state.fieldBlocFromPath('password').asTextFieldBloc.value);

    await Future<void>.delayed(Duration(seconds: 2));
    yield state.toSuccess();
  }
}

5. Create a Form Widget

You need to create a widget with access to the FormBloc.

In this case I will use BlocProvider for do it.

class LoginForm extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return BlocProvider<LoginFormBloc>(
      create: (context) =>
          LoginFormBloc(),
      child: Builder(
        builder: (context) {
          return Scaffold();
        },
      ),
    );
  }
}

6. Add FormBlocListener for manage form state changes

You need to add a FormBlocListener.

In this example:

• I will show a loading dialog when the state is loading.
• I will hide the dialog when the state is success, and navigate to success screen.
• I will hide the dialog when the state is failure, and show a snackBar with the error.

...
          return Scaffold(
            appBar: AppBar(title: Text('Simple login')),
            body: FormBlocListener<LoginFormBloc, String, String>(
              onSubmitting: (context, state) => LoadingDialog.show(context),
              onSuccess: (context, state) {
                LoadingDialog.hide(context);
                Navigator.of(context).pushReplacementNamed('success');
              },
              onFailure: (context, state) {
                LoadingDialog.hide(context);
                Notifications.showSnackBarWithError(
                    context, state.failureResponse);
              },
              child: 
              ),
            ),
          );
...          

7. Connect the Field Blocs with Field Blocs Builder

You need to use a BlocBuilder with the FormBloc, then you can access to each field bloc by using state.fieldBlocFromPath('path').

In this example I will use TextFieldBlocBuilder for connect with email field and password field of LoginFormBloc.

...
              child: BlocBuilder<LoginFormBloc, FormBlocState>(
                builder: (context, state) {
                  return ListView(
                    physics: ClampingScrollPhysics(),
                    children: <Widget>[
                      TextFieldBlocBuilder(
                        textFieldBloc: state.fieldBlocFromPath('email'),
                        keyboardType: TextInputType.emailAddress,
                        decoration: InputDecoration(
                          labelText: 'Email',
                          prefixIcon: Icon(Icons.email),
                        ),
                      ),
                      TextFieldBlocBuilder(
                        textFieldBloc: state.fieldBlocFromPath('password'),
                        suffixButton: SuffixButton.obscureText,
                        decoration: InputDecoration(
                          labelText: 'Password',
                          prefixIcon: Icon(Icons.lock),
                        ),
                      ),
                    ],
                  );
                },
              ),
...          

8. Add a widget for submit the FormBloc

In this example I will add a RaisedButton and pass submit method of FormBloc to submit the form.

...
              child: ListView(
                children: <Widget>[
                  ...,
                  Padding(
                    padding: const EdgeInsets.all(8.0),
                    child: RaisedButton(
                      onPressed: formBloc.submit,
                      child: Center(child: Text('LOGIN')),
                    ),
                  ),
                ],
              ),
...          

Credits

This package uses the following packages:

• form_bloc
• flutter_bloc
• flutter_typeahead
• rxdart
• keyboard_visibility