Simplify Form Controls in Flutter with the FForm Package 🚀

Alexander Bangert — Fri, 13 Sep 2024 17:58:02 +0000

Getting Started with FForm 🌟

Step 1: Installation

First things first, let's get the FForm package into your Flutter project. Add FForm to your pubspec.yaml file under dependencies:

dependencies:
  fform: ^latest_version

Don't forget to run flutter pub get in your terminal to install the package.

Overview

FForm is a high-level Flutter package designed to make form creation and management a breeze, with simplified field validation. It offers two main components: FFormField and FFormBuilder, that together bring ease and flexibility to your form handling in Flutter apps.

FFormField<T, E>: A base class for all form fields supporting values, on-the-fly validation, and change handling.
FFormBuilder<F extends FForm>: A widget that constructs and manages the form state, utilizing streams to refresh the UI dynamically as data changes.
FForm: A base class for creating custom form classes, allowing you to add specific methods and properties to your forms.
FFormException: A base class for creating custom exceptions for form fields, enabling you to define custom validation rules and error messages.
FFormProvider: A widget that allows you to access the form in the widget tree without passing it as a parameter.

Why It Rocks 🎸

State Management Simplified: Automatically handles the state of both individual form fields and the form as a whole.
Built-in Validation with a Twist: Supports on-the-fly validation and error handling for each field, ensuring a smooth user experience.
Flexibility at Its Finest: Supports any data type for field values and validation errors thanks to generics.
Reactive Forms for the Win: Leverages streams for tracking form state changes, ensuring your UI is always in sync.
Multiple Forms, No Problem: Create multiple forms with custom fields and validation rules, all managed seamlessly by FForm.
Custom Exceptions for Custom Needs: Define custom exceptions for form fields to handle complex validation rules and error messages with ease.

Previews

Login Form	Add Forms to Multiple Form	Infinity Forms

Usage Examples

`FFormField`

FFormField is a base class for all form fields, supporting values, on-the-fly validation, and change handling. It provides a set of getters and methods to manage the field state, including checking the field's validity, retrieving the current value, and handling exceptions.

Example

enum EmailError {
  empty,
  not;

  @override
  String toString() {
    switch (this) {
      case empty:
        return 'emailEmpty';
      case not:
        return 'invalidFormatEmail';
      default:
        return 'invalidFormatEmail';
    }
  }
}

class EmailField extends FFormField<String, EmailError> {

  EmailField({required String value}) : super(value);

  @override
  EmailError? validator(value) {
    if (value.isEmpty) return EmailError.empty;
    return null;
  }
}

`FFormField` API

GlobalKey key	A unique key for identifying the form field widget. It is used to manage the state of the widget and to access it in the widget tree.
GlobalKey key

Getters / Setters	Description
T get value	Retrieves the current value of the form field.
set value(T newValue)	Sets a new value for the form field and triggers listeners if the value changes.
E? get exception	Retrieves the current validation exception of the form field, if any.
bool get isValid	Checks if the form field is valid based on the current value and validation rules.
bool get isInvalid	Checks if the form field is invalid based on the current value and validation rules.

Methods	Description
void addListener(FFormFieldListener listener)	Adds a listener that will be called when the value of the form field changes.
void removeListener(FFormFieldListener listener)	Removes a previously added listener from the form field.
E? validator(T value)	Validates the current value of the form field and returns an exception if the value is invalid.

`FForm`

FForm is a base class for creating custom form classes with specific fields and validation rules. It provides a set of getters and methods to manage the form state, including checking the form's validity, retrieving answers, and handling exceptions.

Example

This is a simple example of how to create a form with a single field. You can extend the FForm class to create custom forms with specific fields and validation rules.

class LoginForm extends FForm {
  EmailField email;

  LoginForm({
    required this.email,
  });

  @override
  List<FFormField> get fields => [email];
}

This is a more complex example of how to create a form with multiple fields. You can extend the FForm class to create custom forms with specific fields and validation rules.

class Form extends FForm {
  List<Form> forms;

  Form({
    required this.forms,
  });

  @override
  List<FFormField> get subForms => forms;
}

allFieldUpdateCheck is a property in FForm that determines whether every field update triggers a rebuild of the FFormBuilder. When set to true, the form will rebuild on every field update, ensuring real-time feedback to the user. When set to false, the form will only rebuild when the isValid or isInvalid getters are invoked, reducing the number of rebuilds and enhancing performance.

class LoginForm extends FForm {
  EmailField email;

  LoginForm({
    required this.email,
  });

  @override
  bool get allFieldUpdateCheck => true;

  @override
  List<FFormField> get fields => [email];
}

`FForm` API

Getters	Description
bool get hasCheck	Returns whether the form has any validation checks. This getter checks if there are any validation rules applied to the form fields.
bool get allFieldUpdateCheck	Indicates if every field update triggers a rebuild of the `FFormBuilder`. This is used to determine if the form should be rebuilt on every field update.
List get fields	Retrieves the list of form fields in the form. This getter is used to access all the fields that are part of the form.
List get subForms	Retrieves the list of sub-forms within the form. This is used when the form contains nested forms, allowing access to those sub-forms.
List get answers	Retrieves the list of answers from the form fields. This getter collects the current values of all form fields.
List get exceptions	Retrieves the list of validation exceptions from the form fields. This is used to gather all validation errors present in the form fields.
bool get isValid	Checks if the entire form is valid based on the current values and validation rules. This getter evaluates the validity of the form by checking each field's validation status and calls `notifyListeners()`.
bool get isInvalid	Checks if the entire form is invalid based on the current values and validation rules. This is the inverse of `isValid` and is used to quickly determine if the form has any invalid fields.
FFormField? get firstInvalidField	Retrieves the first invalid form field, if any. This getter is used to find the first field that fails validation.
FFormField? get lastInvalidField	Retrieves the last invalid form field, if any. This getter is used to find the last field that fails validation.

Methods	Description
void addListener(FFormListener listener)	Adds a listener that will be called when the form's state changes. This is useful for updating the UI or performing actions when the form's state changes.
void removeListener(FFormListener listener)	Removes a previously added listener from the form. This is useful for cleaning up listeners when they are no longer needed.
void notifyListeners()	Notifies all registered listeners of a change in the form's state. This is used to trigger updates in the UI or other parts of the application that depend on the form's state.
T get()	Retrieves the first field of a specific type from the form. This is useful for accessing specific fields without knowing their exact position in the form.

`FFormBuilder`

FFormBuilder is a widget that constructs and manages the form state, utilizing streams to refresh the UI dynamically as data changes. It provides a builder function that takes the form and returns a widget tree based on the form's state.

Example

This is an example of how to use FFormBuilder to create a form with a single field. The builder function takes the form as a parameter and returns a widget tree based on the form's state.

void _submit() {
  if(_form.isValid) { // .isValid or .isInvalid start rebuild in FFormBuilder and returned boolean
    print('Form Valid');
  };
}

@override
Widget build(BuildContext context) {
  return FFormBuilder<LoginForm>(
    form: _form,
    builder: (context, form) {
      EmailField email = form.email; // or FFormProvider.of<LoginForm>(context).get<NameField>()

      return Column(
        children: [
          TextField(
            key: email.key,
            controller: _emailController,
            decoration: InputDecoration(
              labelText: 'Email',
              errorText: email.exception.toString(),
            ),
          ),
          ElevatedButton(
            onPressed: _submit,
            child: const Text('Submit'),
          ),
        ],
      );
    },
  );
}

`FFormProvider`

FFormProvider is a widget that allows you to access the form in the widget tree without passing it as a parameter.

Example

FFormBuilder<LoginForm>(
  form: _form,
  builder: (context, form) {

    FFormProvider.of<LoginForm>(context).email; // or form.email;
    FFormProvider.of<LoginForm>(context).get<NameField>(); // or form.get<NameField>();

    return YourForm();
  },
)

FFormException

FFormException is a base class for creating custom exceptions for form fields. It allows you to define custom validation rules and error messages for form fields, enabling you to handle complex validation scenarios with ease.

Example

You can create a custom exception class that extends FFormException to define specific validation rules and error messages for a form field.

class PasswordValidationException extends FFormException {
  final bool isMinLengthValid;
  final bool isSpecialCharValid;
  final bool isNumberValid;

  PasswordValidationException({
    required this.isMinLengthValid,
    required this.isSpecialCharValid,
    required this.isNumberValid,
  });

  @override
  bool get isValid => isMinLengthValid && isSpecialCharValid && isNumberValid;
}

class PasswordField extends FFormField<String, PasswordValidationException> {
  PasswordField(String value) : super(value);

  @override
  PasswordValidationException? validator(String value) {
    final validator = FFormValidator(value);
    return PasswordValidationException(
      isMinLengthValid: validator.isMinLength(8),
      isSpecialCharValid: validator.isHaveSpecialChar,
      isNumberValid: validator.isHaveNumber,
    );
  }
}

FFormException API

Getters	Description
bool get isValid	Returns `true` if the form field is valid based on the current value and validation rules.

DEV Community: Alexander Bangert

Simplify Form Controls in Flutter with the FForm Package 🚀

Getting Started with FForm 🌟

Step 1: Installation

Overview

Why It Rocks 🎸

Previews

Usage Examples

FFormField

Example

FFormField API

FForm

Example

FForm API

FFormBuilder

Example

FFormProvider

Example

FFormException

Example

FFormException API

`FFormField`

`FFormField` API

`FForm`

`FForm` API

`FFormBuilder`

`FFormProvider`