fabrik_forms

fabrik_forms is a clean, testable, UI-agnostic form state management system for Flutter. It handles field values, validation, dirty/touched state, and reactive rebuilds — without coupling your logic to any specific widget.

Installation

Add the package to your pubspec.yaml:

dependencies:
  fabrik_forms: ^0.1.0

Then run:

flutter pub get

Import it in your Dart files:

import 'package:fabrik_forms/fabrik_forms.dart';

---

Getting Started

Define your form with typed fields and validators:

final formNotifier = FabrikFormNotifier<String>(
  FabrikForm({
    'email': FabrikField(
      value: '',
      validators: [const EmailValidator()],
    ),
    'password': FabrikField(
      value: '',
      validators: [
        const PasswordValidator(
          requireDigit: true,
          requireSpecialChar: true,
        ),
      ],
    ),
  }),
);

Wrap your UI with FabrikFormBuilder to rebuild reactively:

FabrikFormBuilder<String>(
  formNotifier: formNotifier,
  builder: (context, form, get) {
    final email = get<String>('email');
    final password = get<String>('password');

    return Column(
      children: [
        TextField(
          onChanged: (val) => formNotifier.update('email', val),
          decoration: InputDecoration(
            labelText: 'Email',
            errorText: email.visibleError,
          ),
        ),
        TextField(
          onChanged: (val) => formNotifier.update('password', val),
          obscureText: true,
          decoration: InputDecoration(
            labelText: 'Password',
            errorText: password.visibleError,
          ),
        ),
        ElevatedButton(
          onPressed: () {
            if (form.isValid) {
              submit(form.values);
            } else {
              formNotifier.markAllTouched(); // reveal all errors
            }
          },
          child: const Text('Sign In'),
        ),
      ],
    );
  },
);

---

Field Metadata

Every FabrikField tracks:

Property	Type	Description
value	T	Current field value
error	String?	Active validation error
visibleError	String?	Error shown only after the field is touched
isValid	bool	No active errors
isTouched	bool	User has interacted with the field
isDirty	bool	Value differs from initial

---

Resetting a Form

Call reset() to restore all fields to their initial values and clear all touched/dirty state:

formNotifier.reset();

This is useful for clearing a form after submission or on cancel.

---

Built-in Validators

RequiredValidator

const RequiredValidator()
const RequiredValidator(message: 'Name is required', trim: false)

MinLengthValidator / MaxLengthValidator

const MinLengthValidator(min: 6)
const MaxLengthValidator(max: 100, message: 'Too long')

EmailValidator

const EmailValidator()                          // required by default
const EmailValidator(isRequired: false)         // optional — empty is valid
const EmailValidator(invalidMessage: 'Bad email')

PasswordValidator

const PasswordValidator()                       // requires 8+ chars, non-empty
const PasswordValidator(isRequired: false)      // optional password
const PasswordValidator(
  minLength: 12,
  requireUppercase: true,
  requireDigit: true,
  requireSpecialChar: true,
)

UrlValidator

const UrlValidator()                            // accepts http and https
const UrlValidator(requireHttps: true)          // https only
const UrlValidator(isRequired: false)           // optional — empty is valid

PhoneValidator

const PhoneValidator()                          // required by default
const PhoneValidator(isRequired: false)         // optional — empty is valid
// Accepts: +1 234 567 8900 · (123) 456-7890 · 123-456-7890 · 1234567890

RangeValidator

const RangeValidator(min: 1, max: 100)
const RangeValidator(min: 0.0, max: 1.0, minMessage: 'Too low', maxMessage: 'Too high')

Custom Validators

Extend FabrikValidator<T> to create your own:

class UsernameValidator extends FabrikValidator<String> {
  const UsernameValidator();

  @override
  String? call(String value) {
    if (value.contains(' ')) return 'No spaces allowed';
    return null;
  }
}

---

Features

• Field-level validation with reusable, composable validators
• Form-level state: .isValid, .isDirty, .isTouched, .values, .errors
• markAllTouched() to reveal all errors on submit
• reset() to restore initial state
• ValueNotifier-based reactivity with FabrikFormNotifier
• Declarative UI with FabrikFormBuilder
• Works independently of the widget tree — fully unit-testable