EO-Color logo

EO principles respected here DevOps By

pub license PDD status

build codecov CodeFactor Grade style: lint Hits-of-Code



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

  • An 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 a required field; ReqEmail for a non-empty, well-formed email; Len.max for a maximum number of characters; and so on.
  • Easy-to-compose validators: e.g. the command Trim(Email()) produces a validator that trims the entered email before validating it.
  • You can apply multiple validation rules at once by using the Pair or Rules classes.
  • Write Less and Do More: built-in, ready-to-use set of compound validators. E.g. to validate an email limited to, say, 50 chars, simply pass an instance of Email.len(50) or ReqEmail.len(50) as the validation argument.

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

Getting Started

A flexible package provides components that can be selected and grouped in various combinations so that user requirements can be fulfilled.

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

  Widget build(BuildContext context) {
    return TextFormField(
      validator: Rules<String>([
      keyboardType: TextInputType.emailAddress,

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

  Widget build(BuildContext context) {
    return TextFormField(
      validator: ReqEmail.len(50),
      keyboardType: TextInputType.emailAddress,

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.):

Grouped by Category

  • brazil — validators related to Brazil (Cep, Cnpj, Cpf, etc).
  • core — core validators (Len, Pair, Req, Rules, Trim, etc).
  • logic — validation logic and unit testing (Equal, Ok, Nok, ValueBack, etc).
  • net — internet (Email, Ipv4, Ipv6, Mac, Url, etc).
  • numeric — validators related to numbers or digits (Digit, Hex, 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
cd formdator/example/
flutter run -d chrome

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




Brazil-related validators. [...]
The package's core validators.
FormdatorFormidable Validator. [...]
Validation logic and unit testing.
Internet related validators. [...]
Validators related to numbers or digits. [...]