formdator
Contents
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
Reqfor required fields;ReqEmailfor non-empty, well-formed emails;Lenfor length constraints;Intfor 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
PairorRulesclasses. - 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.):
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.
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