form_builder_validators 8.1.1

This package provides common reusable FormFieldValidators for Flutter FormField widgets with internationalization

FormBuilder Validators

Form Builder Validators provide a convenient way of validating data entered into any Flutter FormField. It offers common validation rules out of the box (such as required, email, number, min, max, minLength, maxLength, date validations, etc.) and a way to compose multiple validation rules into one FormFieldValidator.

Also included is the l10n / i18n of error text messages to multiple languages.

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Migrating from version 7 to 8

To migrate from v7 to v8, remove context as a parameter to validator functions. For example, FormBuilderValidators.required(context) becomes FormBuilderValidators.required() without context passed to it.

Example

import 'package:form_builder_validators/form_builder_validators.dart';

...

TextFormField(
  decoration: InputDecoration(labelText: 'Name'),
  autovalidateMode: AutovalidateMode.always,
  validator: FormBuilderValidators.required(),
),
TextFormField(
  decoration: InputDecoration(labelText: 'Age'),
  keyboardType: TextInputType.number,
  autovalidateMode: AutovalidateMode.always,
  validator: FormBuilderValidators.compose([
    FormBuilderValidators.numeric(errorText: 'La edad debe ser numérica.'),
    FormBuilderValidators.max(70),
    (val) {
      var number = int.tryParse(val ?? '');
      if (number != null) if (number < 0)
        return 'We cannot have a negative age';
      return null;
    }
  ]),
),

Built-in Validators

This package comes with several most common FormFieldValidators such as required, numeric, mail, URL, min, max, minLength, maxLength, IP, credit card, etc., with default errorText messages.

Available built-in validators include:

• FormBuilderValidators.creditCard() - requires the field's value to be a valid credit card number.
• FormBuilderValidators.date() - requires the field's value to be a valid date string.
• FormBuilderValidators.email() - requires the field's value to be a valid email address.
• FormBuilderValidators.equal() - requires the field's value be equal to provided object.
• FormBuilderValidators.integer() - requires the field's value to be an integer.
• FormBuilderValidators.ip() - requires the field's value to be a valid IP address.
• FormBuilderValidators.match() - requires the field's value to match the provided regex pattern.
• FormBuilderValidators.max() - requires the field's value to be less than or equal to the provided number.
• FormBuilderValidators.maxLength() - requires the length of the field's value to be less than or equal to the provided maximum length.
• FormBuilderValidators.min() - requires the field's value to be greater than or equal to the provided number.
• FormBuilderValidators.minLength() - requires the length of the field's value to be greater than or equal to the provided minimum length.
• FormBuilderValidators.numeric() - requires the field's value to be a valid number.
• FormBuilderValidators.required() - requires the field have a non-empty value.
• FormBuilderValidators.url() - requires the field's value to be a valid url.

Composing multiple validators

FormBuilderValidators class comes with a very useful static function named compose() which takes a list of FormFieldValidator functions. Composing allows you to create once and reuse validation rules across multiple fields, widgets, or apps.

On validation, each validator is run, and if any one validator returns a non-null value (i.e., a String), validation fails, and the errorText for the field is set as the returned string.

Example:

TextFormField(
  decoration: InputDecoration(labelText: 'Age'),
  keyboardType: TextInputType.number,
  autovalidateMode: AutovalidateMode.always,
  validator: FormBuilderValidators.compose([
    /// Makes this field required
    FormBuilderValidators.required(),

    /// Ensures the value entered is numeric - with custom error message
    FormBuilderValidators.numeric(errorText: 'La edad debe ser numérica.'),

    /// Sets a maximum value of 70
    FormBuilderValidators.max(70),

    /// Include your own custom `FormFieldValidator` function, if you want
    /// Ensures positive values only. We could also have used `FormBuilderValidators.min(0)` instead
    (val) {
      final number = int.tryParse(val);
      if (number == null) return null;
      if (number < 0) return 'We cannot have a negative age';
      return null;
    }
  ]),
),

l10n

To allow for localization of default error messages within your app, add FormBuilderLocalizations.delegate in the list of your app's localizationsDelegates

  return MaterialApp(
      supportedLocales: [
        Locale('de'),
        Locale('en'),
        Locale('es'),
        Locale('fr'),
        Locale('it'),
        ...
      ],
      localizationsDelegates: [
        GlobalMaterialLocalizations.delegate,
        GlobalWidgetsLocalizations.delegate,
        FormBuilderLocalizations.delegate,
      ],

Supported languages (default errorText messages)

• Arabic (ar)
• Bangla (bn)
• Catalan (ca)
• Chinese Simplified (zh_Hans)
• Chinese Traditional (zh_Hant)
• English (en)
• Estonian (et)
• Dutch (nl)
• Farsi/Persian (fa)
• French (fr)
• German (de)
• Hungarian (hu)
• Indonesian (id)
• Italian (it)
• Japanese (ja)
• Korean (ko)
• Lao (lo)
• Polish (pl)
• Portuguese (pt)
• Romanian (ro)
• Russian (ru)
• Slovak (sk)
• Slovenian (sl)
• Spanish (es)
• Swahili (sw)
• Ukrainian (uk)

And you can still add your custom error messages.

Support

Issues and PRs

Any support in reporting bugs, answering questions, or PRs is always appreciated.

We especially welcome efforts to internationalize/localize the package by translating the default validation errorText strings for built-in validation rules.

Localizing messages

1. Add ARB files

Create one ARB file inside the lib/l10n folder for each of the locales you need to add support. Name the files in the following way: intl_<LOCALE_ISO_CODE>.arb. For example: intl_fr.arb or intl_fr_FR.arb.

2. Translate the error messages

Duplicate the contents of intl_messages.arb (or any other ARB file) into your newly created ARB file, then translate the error messages by overwriting the default messages.

3. Run command

To generate boilerplate code for localization, run the generate command inside the package directory where pubspec.yaml file is located:

  flutter pub run intl_utils:generate

Running the command will automatically create/update files inside the lib/localization directory, including your newly added locale support.

4. Update README

Remember to update README, adding the new language (and language code) under Supported languages section so that everyone knows your new language is now supported!

5. Submit PR

Submit your PR and be of help to millions of developers all over the world!

Coffee :-)

If this package was helpful to you in delivering your project, or you want to support this package, I would highly appreciate a cup of coffee ;-)