formdator 0.12.3

A collection of form field validators that can be selected and grouped into various combinations through composition — Decorator Pattern.

formdator

Contents

• Overview
• Getting Started
• List of Validators
  • Categories
• Demo Application
• References

Overview

Form Validator — Formdator is a fully object-oriented package for validating Flutter form fields. Its main benefits, compared to all other similar packages, include:

• Dependency-free: there is only pure Dart code.
• Object-oriented mindset: the elements for validation are immutable objects that can be combined in various configurations.
• Classes with short — yet meaningful — names like Req for required fields; ReqEmail for non-empty, well-formed emails; Len for length constraints; Int for integer-only values; and so on.
• Easy-to-compose validators: e.g., the command Trim(Email()) produces a validator that trims an email value before validating it.
• Multiple validation at once: you can apply multiple validation rules at once by using the Pair or Rules classes.
• Built-in set of compound validators: e.g., to validate an email and limit its length to a maximum of 50 characters, simply use an instance of Email.len(50) — write less; do more!

For easier integration with Flutter form fields, every validator implements the call() method. As a result, any validator object can be called as a function — Callable Classes.

Getting Started

The following code snippet demonstrates how you can easily group the Rules, Req, Len and Email classes together to create a kind of 'email-max-50-characters' constraint.

  @override
  Widget build(BuildContext context) {
    return TextFormField(
      validator: Rules<String>([ // The "Rules" class performs multiple validations at once.
        Req(blank: 'Please enter the email'), // "blank" is the error message in case of field left blank.
        Len.max(50, long: 'Email length cannot exceed 50 characters'), // "long" is the error message if an input value is too long.
        Email(mal: 'Malformed email'), // "mal" is the error message in case of malformed email.
      ]),
    );
  }

Or — even better — use the compound validator ReqEmail to perform the same task.

  @override
  Widget build(BuildContext context) {
    return TextFormField(
      validator: ReqEmail.len(
        50,
        blank: 'Please enter the email',
        mal: 'Malformed email',
        long: 'Email length cannot exceed 50 characters',
      ),
    );
  }

The shorter command ReqEmail.len(50) is equivalent to the much longer command Rules<String>([Req(), Len.max(50), Email()]) — write less; do more!

List of Validators

For a complete list of validators with detailed information about each one (constructors, parameters, etc.):

• formdator-library.

Grouped by Category

• brazil — validators related to Brazil (BrMobile, BrPhone, Cep, Cnpj, Cpf, etc.).
• core — core validators (Len, Match [text pattern], Pair, Req, Rules, Trim, etc.).
• logic — validation logic and unit testing (Equal, Ok, Nok, ValueBack).
• net — internet (Email, Ipv4, Ipv6, MacAddr, Url, etc.).
• numeric — validators related to numbers or digits (Digit, Hex, Int, Num, etc.).

Demo application

The demo application provides a fully working example, focused on demonstrating exactly four validators in action — Pair, ReqLen, ReqEmail, and Equal. You can take the code in this demo and experiment with it.

To run the demo application:

git clone https://github.com/dartoos-dev/formdator.git
cd formdator/example/
flutter run -d chrome

This should launch the demo application on Chrome in debug mode.

References

• Dart Callable classes
• TextFormField
• build a Flutter form
• Mozilla input types
• brazilian form masks