Form Validator

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A library to validate form fields for Flutter framework


Contains(String seed, String message)check if the string contains the seed.
Equals(String seed, String message)check if the field value equal to a certain string
Required(String message)Mark the field is required.
MaxLength(int limit, String message)Set the maximum amount of character.
MinLength(int limit, String message)Set the minimum amount of character.
Between(String message, {int max, int min})Limit the field digits to be between limited range

it use MaxLength and MinLength validators.

the message argument is required here
Composs(String message, List validators)Composs multiple validator into one singular validator.

the message argument is required here
Email(String message, String regexp)Indicate that the field should be an email

It uses a common regexp to validate the string, but you can use your own

the regexp is r"^[a-zA-Z0-9.]+@[a-zA-Z0-9]+\.[a-zA-Z]+"]

Pattern(String regexp, String message) | check if the field value matches the pattern. CreditCardCVCValidator(String message) | cvc/cvv card validator CreditCardNumberValidator(String message) | credit card number validator CreditCardMonthValidator | credit card date validator


Invoke validate function to execute the list of predefined validators

        validator: validate([
            Required('This field is required'),
            Email('Please enter the email correctly'),

and the result will be getting by setting autovalidate property, using global key of the Form widget or the Form Field, click Here for more information about flutter validation.

please note that the validators functions will be executed in the same order that was defined

the validators are simple functions that returns true when the value is not as supposed so you can build your validators the works the same as the predefined ones

    class CustomValidator implements IValidator {
        final String message = 'Message to be used as error message';
        call(String value) {
            return ("if meets my condition") ? false : true;

also, you can always see the source code to learn more.

The last thing that you can use a 3rd lib to facilitate the process, you can see this one, here's one of it's function isDate() that validates if the string is date, because it's a function that returns boolean we can use it with our interface to form a validator function, like this:

    class IsDate implements IValidator {
        final String message = 'Message to be used as error message';
        call(String value) {
            return isDate(value);

        key: myFormKey,
        validator: validate([
            IsDate('Please enter correct date')


Don't hesitate to open issues and make a pull request to help improve code

  1. Fork it!
  2. Create your feature branch: git checkout -b my-new-feature
  3. Commit your changes: git commit -m 'Add some feature'
  4. Push to the branch: git push origin my-new-feature
  5. Submit a pull request :D


This library will be maintained under the semantic versioning guidelines. Releases will be numbered with the following format: <major>.<minor>.<patch>

For more information on SemVer, please visit




The MIT License (MIT)