Formz 📝 #

A unified form representation in Dart. Formz aims to simplify form representation and validation in a generic way.

Create a FormzInput #

import 'package:formz/formz.dart';

// Define input validation errors
enum NameInputError { empty }

// Extend FormzInput and provide the input type and error type.
class NameInput extends FormzInput<String, NameInputError> {
  // Call super.pure to represent an unmodified form input.
  const NameInput.pure() : super.pure('');

  // Call super.dirty to represent a modified form input.
  const NameInput.dirty({String value = ''}) : super.dirty(value);

  // Override validator to handle validating a given input value.
  @override
  NameInputError validator(String value) {
    return value?.isNotEmpty == true ? null : NameInputError.empty;
  }
}

Interact with a FormzInput #

final name = NameInput.pure();
print(name.value); // ''
print(name.valid); // false
print(name.status); // FormzInputStatus.pure
print(name.error); // NameInputError.empty

final joe = NameInput.dirty(value: 'joe');
print(joe.value); // 'joe'
print(joe.valid); // true
print(joe.status); // FormzInputStatus.valid
print(joe.error); // null
print(joe.toString()); // NameInput('joe', true);

Validate Multiple FormzInput Items #

final validInputs = <FormzInput>[
  NameInput.dirty(value: 'jan'),
  NameInput.dirty(value: 'jen'),
  NameInput.dirty(value: 'joe'),
];

print(Formz.validate(validInputs)); // FormzStatus.valid

final invalidInputs = <FormzInput>[
  NameInput.dirty(value: ''),
  NameInput.dirty(value: ''),
  NameInput.dirty(value: ''),
];

print(Formz.validate(invalidInputs)); // FormzStatus.invalid

Automatic FormzStatus Computation #

class LoginForm with FormzMixin {
  LoginForm({
    this.username = const Username.pure(),
    this.password = const Password.pure(),
  });

  final Username username;
  final Password password;

  @override
  List<FormzInput> get inputs => [username, password];
}

final form = LoginForm();
print(form.status); // FormzStatus.pure