how to use

first if you are using localizations you must add localization delegate to your material app or we will use arabic

  return MaterialApp(
    localizationsDelegates: [
      ReadyValidationMessages.delegate,
      ...other delegates
    ],
    home: MyApplicationHome(),
  );

if you want to use specified messages across the app you can do so

ValidationMessagesConfig(
  messages: ReadyValidationMessagesAr(),
  child: // screen or material app
);

don't worry every validation has a parameter for custom message

usage

/// its very simple

TextFormField(

    validator: context
        .string()
        .required()
        .notEmpty()
        .hasMaxLength(10)
        .hasMinLength(15)
        .isNumber()
        .greaterThan(10),

  );

explanation

it get the validator for String? values
it check if the value is not null and convert the validator to String instead of String?

at this point we can use non nullable string validations
checks that string is not empty
check the max length of string
check the min length of string
check if string is number and if it pass transform validator to num validator

at this point we can use all number validations like greaterThan
check if the transformed number is greater than 10
is any of the validations fails it will return its validation message and will not continue validations

non context validation

BuildContext is used to apply localization and global config localization but some times you need to check if is valid this is also supported and this time you don't need to validate required is the value is non nullable as we already know its not null

 var number = "7";

  var isValid = number
      .validateWith((v) => v.isNumber())
      .validateWith((v) => v.isBetween(5, 10))
      .isValid();

  /// or
  isValid = number.validateWith((v) => v.isNumber().isBetween(5, 10)).isValid();

  // ignore: avoid_print
  print(isValid);

Available validations

all types

required notEqual equal isIn isNotIn validateWith

strings

isEmail isCreditCard startsWith contains endsWith notEmpty notEmptyOrWhiteSpace matches hasLength hasMinLength
hasMaxLength hasRange isAngelCompany isAngelJob isCrunchbaseOrganization isCrunchbasePerson isFacebookUrl isGitHubUrl
isGooglePlusUrl isHackerNewsUserUrl isHackerNewsItemUrl isInstagramUrl isLinkedInProfile isLinkedInCompany isLinkedInPost
isRedditUrl isSnapchatUrl isStackexchangeUrl isStackoverflowQuestionUrl isStackoverflowUserUrl isTelegramProfileUrl isMediumPostUrl
isMediumUserUrl isTwitterStatusUrl isTwitterUserUrl isYoutubeChannelUrl isYoutubeVideoUrl isYoutubeUserUrl

numbers

lessThan greaterThan isBetween lessThanOrEqual greaterThanOrEqual isBetweenOrEqual isDivisibleBy
isNegative isPositive isEven isOdd

dates

isAfter isAfterOrEqual isBefore isBeforeOrEqual isBetween isBetweenOrEqual

note : most of the validators has an alternatives with prefix Fn like startsWithFn which accepts function instead of value

validators

  /// string validators
  context.string();

  /// number validators
  context.number();

  /// integer validators
  context.integer();

  /// decimal validators
  context.decimal(); // for doubles

  /// boolean validators
  context.boolean();

   /// dateTime validators
  context.dateTime();

    /// dateTime validators
  context.timeOfDay(); // will be added soon

  /// list validators
  context.list<T>(); 

  /// map validators
  context.map<K,V>(); 

  /// other validators
  context.validator<T>();

transforming

in any step you can transform your validator to another type and it can still be used with field

imagine we created a validator for our TextFormField which accepts a validator of type string

so our validator will be

  context.string();

now we need to transform it number validator

       context
        .string()
        .required() // this to ensure it not null
        .transform((v)=>int.parse(v))

now you can use any number validation like greaterThan but you cant use hasMaxLength as it for string till you transform its again to the string validator

when , whenNot , allWhen , allWhenNot

context
        .string()
        .required()
        .hasMaxLength(10)
        .hasMinLength(15)
        .when((x) => false) /// at this point `hasMinLength` is ignored
        .isNumber()
        .greaterThan(10),
  /// so the validations will be
  /// `required` => `hasMaxLength` => `isNumber` => `greaterThan`

Advanced

Some times you want to use your own messages to that you has to create your own delegate and classes

the default delegate look like this


class _ReadyValidationMessagesDelegate
    extends LocalizationsDelegate<ReadyValidationMessages> {
  const _ReadyValidationMessagesDelegate();

  @override
  Future<ReadyValidationMessages> load(Locale locale) {
    return SynchronousFuture<ReadyValidationMessages>(
        lookupReadyValidationMessages(locale));
  }

  @override
  bool isSupported(Locale locale) =>
      <String>['ar', 'en', 'fr', 'ur'].contains(locale.languageCode);

  @override
  bool shouldReload(_ReadyValidationMessagesDelegate old) => false;
}

ReadyValidationMessages lookupReadyValidationMessages(Locale locale) {
  // Lookup logic when only language code is specified.
  switch (locale.languageCode) {
    case 'ar':
      return ReadyValidationMessagesAr();
    case 'en':
      return ReadyValidationMessagesEn();
    case 'fr':
      return ReadyValidationMessagesFr();
    case 'ur':
      return ReadyValidationMessagesUr();
  }

  throw FlutterError(
      'ReadyValidationMessages.delegate failed to load unsupported locale "$locale". This is likely '
      'an issue with the localizations generation tool. Please file an issue '
      'on GitHub with a reproducible sample app and the gen-l10n configuration '
      'that was used.');
}

you also need to create your custom ReadyValidationMessages classes now instead of using our delegate use your own

  return MaterialApp(
    localizationsDelegates: [
      CustomReadyValidationMessages(),
      ...other delegates
    ],
    home: MyApplicationHome(),
  );

injectable

what if you need to make your own validation that can be used with other validations -like this


TextFormField(

    validator: context
        .string()
        .required()
        .myCustomValidation() /// this your custom validation
        .hasMaxLength(10)
        .hasMinLength(15)
        .isNumber()
        .greaterThan(10),

  );

to do this you have to extend the field validator


extension MyCustomValidationExtension<T> on FieldValidator<T, String> {
  FieldValidator<T, String> myCustomValidation() {
    return next(
      (messages, value) => !validate(value)/// validate your text here
          ? "My custom message"
          : null,
    );
  }
}

/// FieldValidator takes 2 generic arguments
/// the first is the caller which means what is the type of value that will be passed to the validator
/// as we need our validator to work with string values and any type that is transformed to string we use T as the first arg