form_validator_kit #

A lightweight and composable Flutter form validation package with clean, reusable validators for common form fields.

form_validator_kit helps keep validation logic out of your widget tree while still feeling simple to read and easy to customize.

Features #

• Built-in validators for common form use cases
• Composable API with FormValidator.combine(...)
• Custom error messages for every validator
• Optional-field support with allowEmpty
• Password rule validation with configurable requirements
• Reusable PasswordInputField widget with polished password UX
• Ready to use with TextFormField.validator

Included Validators #

• required
• email
• phone
• minLength
• maxLength
• exactLength
• password
• confirmPassword
• regex
• url
• username
• numeric
• combine

Installation #

Add the package to your pubspec.yaml:

dependencies:
  form_validator_kit: ^0.0.1

Then run:

flutter pub get

Import #

import 'package:form_validator_kit/form_validator_kit.dart';

Quick Start #

TextFormField(
  decoration: const InputDecoration(labelText: 'Email'),
  validator: FormValidator.combine([
    FormValidator.required(),
    FormValidator.email(),
  ]),
)

Password Widget #

The package also ships with a reusable PasswordInputField that includes:

• show and hide toggle
• password strength indicator
• live validation hints
• caps lock warning styling
• confirm password matching

PasswordInputField(
  controller: passwordController,
  validator: FormValidator.required(),
  minLength: 8,
  requireUppercase: true,
  requireLowercase: true,
  requireNumber: true,
  requireSpecialChar: true,
)

PasswordInputField(
  controller: confirmPasswordController,
  labelText: 'Confirm Password',
  validator: FormValidator.required(),
  matchController: passwordController,
  validateAgainstPolicy: false,
  showStrengthIndicator: false,
)

Usage Examples #

Required #

TextFormField(
  validator: FormValidator.required(),
)

Email #

TextFormField(
  validator: FormValidator.email(),
)

Optional Email #

Useful when a field is optional but still needs to be valid when filled:

TextFormField(
  validator: FormValidator.email(allowEmpty: true),
)

Combined Validators #

TextFormField(
  validator: FormValidator.combine([
    FormValidator.required(message: 'Email is required'),
    FormValidator.email(),
  ]),
)

Password #

TextFormField(
  obscureText: true,
  validator: FormValidator.password(
    minLength: 8,
    requireUppercase: true,
    requireLowercase: true,
    requireNumber: true,
    requireSpecialChar: true,
  ),
)

Confirm Password #

TextFormField(
  obscureText: true,
  validator: (value) => FormValidator.confirmPassword(
    passwordController.text,
  )(value),
)

Regex #

TextFormField(
  validator: FormValidator.regex(
    RegExp(r'^[A-Z]{3}\d{3}$'),
    message: 'Enter a valid code',
  ),
)

Username #

TextFormField(
  validator: FormValidator.username(
    minLength: 4,
    maxLength: 16,
  ),
)

Numeric Range #

TextFormField(
  validator: FormValidator.numeric(
    min: 18,
    max: 65,
  ),
)

URL #

TextFormField(
  validator: FormValidator.url(allowEmpty: true),
)

API Overview #

Default Error Messages #

Examples of the built-in messages:

• This field is required.
• Enter a valid email address.
• Enter a valid phone number.
• Minimum length is 6 characters.
• Maximum length is 20 characters.
• Password must contain at least one uppercase letter.
• Passwords do not match.

You can override any of these with a custom message.

Example App #

A runnable example app is included in the package:

cd example
flutter run

The example demonstrates:

• single validators
• combined validators
• password rules
• reusable password input widget
• confirm password validation
• optional URL validation

Testing #

This package includes unit tests for:

• required validation
• email validation
• phone validation
• length validation
• password validation
• regex validation
• URL validation
• username validation
• numeric validation
• combined validation

Run tests with:

dart test

Why Use form_validator_kit #

• Reduces repeated validation code across projects
• Keeps widget code easier to read
• Makes validation rules consistent across screens
• Works well for both simple forms and larger production apps

Roadmap #

Planned future improvements may include:

• localization support
• async validators
• date validators
• region-specific validation presets

License #

This package is released under the MIT License.