A powerful and flexible Flutter validation library designed to simplify form validation, provide clear user feedback, and support internationalization out of the box.

I basically build this Package so Devs can use

  1. Comprehensive Validators: A rich set of built-in validators for common use cases like emails, passwords, phone numbers, names, URLs, and more.
  2. Easy Integration: Use validators directly within TextFormField or get a simple bool result using isValid methods for any validation logic.
  3. Customizable Messages: Easily override default validation messages globally, per-validator, or for specific fields.
  4. Internationalization (i18n): Built-in support for localization. Default messages are provided in English, with the ability to add and use your own translations.
  5. Multi-language Character Support: Validate names and text in over 25 languages.
  6. Advanced Phone Number Validation: Supports validation for 35+ country codes.
  7. Custom Logic: Chain multiple validation rules together for complex scenarios.

Table of Contents

Getting Started

Installation

Add this to your package's pubspec.yaml file:

dependencies:
  boolean_validation: ^1.1.0

Then, run flutter pub get in your terminal.

Basic Usage

Import the package and use the Validators singleton to access all validation methods.

1. Inside a TextFormField

import 'package:boolean_validation/boolean_validation.dart';
import 'package:flutter/material.dart';

final validators = Validators(); // Access the singleton instance

class MyForm extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return TextFormField(
      autovalidateMode: AutovalidateMode.onUserInteraction,
      decoration: InputDecoration(labelText: 'Email'),
      validator: (value) => validators.userInput.validateEmail(value),
    );
  }
}

2. Direct isValid Checks

For logic outside of forms, every validate... method has a corresponding is...Valid method.

import 'package:boolean_validation/boolean_validation.dart';

class WrapperClass with ValidationLogic {
  final validators = Validators();

// The `isValid` singleton gives you direct access to boolean checks
  if(isValidEmail('someEmail')) {
  print('Email is valid!');
  }

// You can also use the boolean extensions on String
  if (isValidPassword('password')) {
  print('Password is strong enough!');
  }
}

Customization

Global Custom Messages

Override messages globally when your app starts.

import 'package:boolean_validation/boolean_validation.dart';

void main() {
  final messages = ValidationMessages();
  messages.copyWith(invalidEmail: 'This not a valid email');
  
  //Or override the ValidationMessageProvider class
  runApp(MyApp());
}

Per-Field Custom Messages

Provide a custom message directly in the validator method to override any global setting.

TextFormField(
  validator: (value) => validators.userInput.validateEmail(
    value,
    customInvalidMessage: 'That doesn\'t look like an email address.',
    customRequiredMessage: 'We need your email!',
  ),
)

For a complete guide on setting up internationalization with ARB files, please see the example application.

Available Validators

User Input Validators

Validator Description
validateEmail Validates standard email formats.
validateConstrainedEmail Validates an email against a specific domain.
validateMobileNumber Validates a mobile number based on a country's pattern.
validateCreditCard Validates credit card numbers using the Luhn algorithm.
validatePassword Checks for password strength (length, uppercase, digits, special characters).
validateUsername Validates usernames based on length and allowed characters.
validateFullName Ensures the input contains at least two alphabetic words.
validateName Ensures the input contains a single alphabetic word.

Data Type Validators

Validator Description
validateUrl Validates URL formats.
validateDate Validates date strings in YYYY-MM-DD format.
validateInteger Checks if the input is a valid integer.
validateDouble Checks if the input is a valid double/decimal number.
validatePositiveNum Checks if the input is a number greater than zero.
validateAlpha Checks if the string contains only alphabetic characters.
validateAlphanumeric Checks if the string contains only alphanumeric characters.

Location Validators

Validator Description
validateLat Validates a geographic latitude value (-90 to 90).
validateLong Validates a geographic longitude value (-180 to 180).

Advanced Usage & Parameters

Email (Constrained Domain)

String? validateConstrainedEmail(String? value, {
  required EmailDomain domain,
  bool isRequired = true,
  String? customRequiredMessage,
  String? customInvalidMessage,
});
Parameter Type Description
value String? Email to validate
domain EmailDomain Required domain (e.g., EmailDomain.gmail())
customRequiredMessage String? Custom message if the field is empty.
customInvalidMessage String? Custom message if the email format is invalid.

Mobile Number

String? validateMobileNumber(String? value, {
  bool isRequired = true,
  String? customRequiredMessage,
  String? customInvalidMessage,
  String? prefix,
});
Parameter Type Description
value String? Mobile number to validate
prefix String? Country code to validate against (CountryPhonePattern enum)
customRequiredMessage String? Custom message when empty.
customInvalidMessage String? Custom message when invalid.

Password

String? validatePassword(String? value, {
  int minLength = 8,
  bool requireUppercase = true,
  String? customUppercaseMessage,
  bool requireDigit = true,
  String? customDigitMessage,
  bool requireSpecialChar = true,
  String? customSpecialCharMessage,
});
Parameter Type Default Description
value String? - Password to validate
minLength int 8 Minimum required length.
requireUppercase bool true If an uppercase letter is required.
requireDigit bool true If a digit is required.
requireSpecialChar bool true If a special character is required.
custom...Message String? - Custom message for a specific failed validation rule.

Name

String? validateName(String? value, {
  bool isRequired = true,
  String? customRequiredMessage,
  String? customInvalidMessage,
  List<SupportedLanguage> multiLang = const [SupportedLanguage.english],
});
Parameter Type Default Description
value String? – The name input to validate.
multiLang List<SupportedLanguage> [SupportedLanguage.english] List of allowed languages for character validation.
customRequiredMessage String? messages.nameRequired Custom error message if the field is empty.
customInvalidMessage String? messages.nameMustBeAlphabetic Custom error message for invalid characters.

Chaining Validators

Use runMultiValidators for complex scenarios where multiple conditions must be met.

String? validateCustomField(String? value) {
  final success = isValid.runMultiValidators(
    validators: [
      () => isValid.notEmpty(value),
      () => isValid.email(value, domain: EmailDomain.custom('2math.io')),
    ],
  );

  if (!success) {
    return 'Must be a valid email ending in @2math.io';
  }
  return null;
}

Example App

This repository includes a comprehensive example application and live example that demonstrates all major features of the library, including a complete validation form, i18n setup, a language switcher, and a searchable country code dropdown.

Visual Architecture

Note: The diagram below is a static image for compatibility with pub.dev.

Auto Docs Simplified Architecture Diagram

A full, detailed diagram of the package architecture can be found here: Architecture Diagram

Contributing

Contributions are welcome! If you find a bug or have a feature request, please open an issue. If you want to contribute code, please open a pull request.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Libraries

boolean_validation