form_validator

Simplest form validation for flutter form widgets.

• Zero dependency
• Localization supported
• Extensible
• Well tested
• Open source

Example

TextFormField(
  validator: ValidationBuilder().email().maxLength(50).build(),
  decoration: InputDecoration(labelText: 'Email'),
),

Getting Started

Installation

Add form_validator as dependency to your flutter project by adding this lines to pubspec.yaml.

dependencies:
  form_validator: ">=0.1.1 <2.0.0"

Then run flutter pub get to install required dependencies.

Check installation tab for more information

Code

Import form_validator package to your dart widgets by writing:

import 'package:form_validator/form_validator.dart';

Now you can use ValidationBuilder class to create validation logic. Here's simple validator that validates if input length is between 10 and 50 characters long.

final validate = ValidationBuilder().minLength(10).maxLength(50).build();

print(validate('test'));        // Minimum length must be at least 10 characters
print(validate('Hello World')); // null, means value is correct

Localization

You can set global locale using ValidationBuilder.setLocale(String localeName) or you can also define locale on ValidationBuilder({ String localeName }) constructor.

ValidationBuilder.setLocale('en');

// will use *en* localization
ValidationBuilder()
  .minLength(5)
  .build();

// will use *az* localization
ValidationBuilder(localeName: 'az')
  .minLength(5)
  .build();

// will display custom message
ValidationBuilder()
  .minLength(5, 'Length < 5 😟')
  .build();

Methods

.minLength(int minLength, [String message])

Validates if value length is not less than minLength.

.maxLength(int maxLength, [String message])

Validates if value length is not more than maxLength.

.email([String message])

Checks if value is an email address.

.phone([String message])

Checks if value is an phone number.

Note: This method might be changed in future.

.ip([String message])

Checks if value is correct IPv4 address.

.ipv6([String message])

Checks if value is correct IPv6 address.

.url([String message])

Checks if value is correct url address.

.match(String otherValue, [String message])

Checks if the value matches the specified otherValue. This can be used to validate if two input values are identical.

.regExp(RegExp regExp, String message)

Validates if value does matches regExp or not.

message argument is required in this method.

.or(Action<ValidationBuilder> left, Action<ValidationBuilder> right, {bool reverse = false})

Validates if value passes any of left and right validations. If value doesn't passes any error message from right validation will be displayed (If reverse set to true message from left validation will be displayed).

Example:

print(
  ValidationBuilder().or(
    (builder) => builder.email('not email'),
    (builder) => builder.phone('not phone'),
  )
  .test('invalid')
); // not phone

print(
  ValidationBuilder().or(
    (builder) => builder.email('not email'),
    (builder) => builder.phone('not phone'),
    reverse: true,
  )
  .test('invalid')
); // not email

Notes

ValidationBuilder is mutable.

You need to construct different instances for each validation.

Wrong

final builder = ValidationBuilder().email();

TextFormField(
  validator: builder.maxLength(50).build(),
),
TextFormField(
  validator: builder.maxLength(20).build(),
),

Correct

final validator1 = ValidationBuilder().email().maxLength(50).build();
final validator2 = ValidationBuilder().email().maxLength(20).build();

TextFormField(
  validator: validator1,
),
TextFormField(
  validator: validator2,
),

Add custom localization

Firstly you need to extend abstract FormValidatorLocale class.

import 'package:form_validator/form_validator.dart';

class MyValidationLocale extends FormValidatorLocale {
  @override
  String name() => "custom";

  @override
  String required() => "Field is required";

  ...
}

PROTIP: You can copy a language file from /lib/src/i18n folder and modify messages as you want.

Then you can use your custom locale class as global or local validation locale.

// global locale
void main() {
  ValidationBuilder.globalLocale = MyValidationLocale();
  ...
}

// local locale
final locale = MyValidationLocale();

build(BuildContext context) {
  final emailValidator = ValidationBuilder(locale: locale)
    .email()
    .build();
  ...
}

PROTIP: Feel free to add your locale to library by opening pull request TheMisir/form-validator to support library.

Extending ValidationBuilder

You can use dart extension methods to extend ValidationBuilder.

extension CustomValidationBuilder on ValidationBuilder {
  password() => add((value) {
    if (value == 'password') {
      return 'Password should not "password"';
    }
    return null;
  });
}

final validator = ValidationBuilder().password().build();

Support

If you would like to support this library you could translate messages to your own language.