FormValidator class

Validates form field input using a typed rule pipeline.

There are three patterns for building a validator:

1. Named constructor — single rule:

FormValidator.notEmpty()
FormValidator.email()

2. Chainable fluent API — multiple rules:

FormValidator().notEmpty().minLength(3)
FormValidator().email().nullable()

3. Explicit list of FormRule objects:

FormValidator.rule([
  FormRuleNotEmpty(null),
  FormRuleMinLength(3, null),
])

Call .nullable() to skip all rules when the value is null or empty.

Passed to InputField.formValidator; the first failing rule's message is shown beneath the field via InputDecoration.errorText.

Constructors

FormValidator({dynamic data, String? attribute})

Create a new form validator with message and data

FormValidator.beginsWith(String prefix, {String? message})

Validate that the value begins with prefix message The message to display if the value is invalid

FormValidator.booleanFalse({String? message})

Validate a value is a boolean message The message to display if the value is invalid

FormValidator.booleanTrue({String? message})

Validate a value is a boolean message The message to display if the value is invalid

FormValidator.capitalized({String? message})

Validate that the value is capitalized message The message to display if the value is invalid

FormValidator.contains(List<String> values, {String? message})

Validate the value contains one of the values message The message to display if the value is invalid

FormValidator.custom({String? message, required bool validate(dynamic data)})

Validate a custom rule message The message to display if the custom validation fails validate The custom validation function that takes the data and returns a boolean

FormValidator.date({String? message})

Validate that the value is a date message The message to display if the value is invalid

FormValidator.dateAgeIsOlder(int age, {String? message})

Validate that the date is older than age message The message to display if the value is invalid age The age to compare

FormValidator.dateAgeIsYounger(int age, {String? message})

Validate that the date is younger than age message The message to display if the value is invalid age The age to compare

FormValidator.dateInFuture({String? message})

Validate that the date is in the future message The message to display if the value is invalid

FormValidator.dateInPast({String? message})

Validate that the date is in the past message The message to display if the value is invalid

FormValidator.email({String? message})

Validate an email message The message to display if the email is invalid

FormValidator.endsWith(String suffix, {String? message})

Validate that the value ends with suffix message The message to display if the value is invalid

FormValidator.lowercase({String? message})

Validate that the value is lowercase message The message to display if the value is invalid

FormValidator.maxLength(int value, {String? message})

Validate that the value is a maximum of value characters message The message to display if the value is invalid value The maximum number of characters

FormValidator.maxSize(int value, {String? message})

Validate that the value is a maximum size of value message The message to display if the value is invalid value The maximum size

FormValidator.maxValue(int value, {String? message})

Validate that the value is a maximum of value message The message to display if the value is invalid value The maximum value

FormValidator.minLength(int value, {String? message})

Validate that the value is a minimum of value characters message The message to display if the value is invalid value The minimum number of characters

FormValidator.minSize(int value, {String? message})

Validate that the value is a minimum size of value message The message to display if the value is invalid value The minimum size

FormValidator.minValue(int value, {String? message})

Validate that the value is a minimum of value message The message to display if the value is invalid value The minimum value

FormValidator.notEmpty({String? message})

Validate that the value is not empty message The message to display if the value is invalid

FormValidator.numeric({String? message})

Validate that the value is numeric message The message to display if the value is invalid

FormValidator.password({int strength = 1, String? message})

Validate a password with a strength of 1 or 2 strength 1: 1 uppercased letter, 1 digit, 8 characters strength 2: 1 uppercased letter, 1 digit, 1 special character, 8 characters message The message to display if the password is invalid

FormValidator.phoneNumberUk({String? message})

Validate a UK phone number message The message to display if the phone number is invalid

FormValidator.phoneNumberUs({String? message})

Validate a US phone number message The message to display if the phone number is invalid

FormValidator.postcodeUk({String? message})

Validate that the value is a valid postcode for the UK message The message to display if the value is invalid

FormValidator.regex(String regex, {String? message})

Validate that the value matches a regex pattern message The message to display if the value is invalid

FormValidator.rule(List<FormRule> rules, {dynamic data})

Create a validator from an explicit list of FormRule objects.

FormValidator.uppercase({String? message})

Validate that the value is uppercase message The message to display if the value is invalid

FormValidator.url({String? message})

Validate a URL message The message to display if the URL is invalid

FormValidator.zipcodeUs({String? message})

Validate that the value is a valid zipcode for the US message The message to display if the value is invalid

Properties

attribute ↔ String?

getter/setter pair

data ↔ dynamic

getter/setter pair

hashCode → int

The hash code for this object.

no setter, inherited

rules ↔ List<FormRule>

getter/setter pair

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

beginsWith(String prefix, {String? message}) → FormValidator

Validate that the value begins with prefix

booleanFalse({String? message}) → FormValidator

Validate a value is a boolean (must be false)

booleanTrue({String? message}) → FormValidator

Validate a value is a boolean

capitalized({String? message}) → FormValidator

Validate that the value is capitalized

check([dynamic data]) → FormValidationResult

Check the validation of the data against the rules Returns a FormValidationResponse indicating success or error

contains(List<String> values, {String? message}) → FormValidator

Validate the value contains one of the values

custom({String? message, required bool validate(dynamic data)}) → FormValidator

Validate a custom rule message The message to display if the custom validation fails validate The custom validation function that takes the data and returns a boolean

date({String? message}) → FormValidator

Validate that the value is a date

dateAgeIsOlder(int age, {String? message}) → FormValidator

Validate that the date is older than age

dateAgeIsYounger(int age, {String? message}) → FormValidator

Validate that the date is younger than age

dateInFuture({String? message}) → FormValidator

Validate that the date is in the future

dateInPast({String? message}) → FormValidator

Validate that the date is in the past

email({String? message}) → FormValidator

Validate an email

endsWith(String suffix, {String? message}) → FormValidator

Validate that the value ends with suffix

equals(dynamic data, {String? message}) → FormValidator

Validate that the value equals another value

lowercase({String? message}) → FormValidator

Validate that the value is lowercase

maxLength(int value, {String? message}) → FormValidator

Validate that the value is a maximum of value characters

maxSize(int value, {String? message}) → FormValidator

Validate that the value is a maximum size of value

maxValue(int value, {String? message}) → FormValidator

Validate that the value is a maximum of value

minLength(int value, {String? message}) → FormValidator

Validate that the value is a minimum of value characters

minSize(int value, {String? message}) → FormValidator

Validate that the value is a minimum size of value

minValue(int value, {String? message}) → FormValidator

Validate that the value is a minimum of value

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

notEmpty({String? message}) → FormValidator

Validate that the value is not empty

nullable() → FormValidator

Mark this validator as nullable. When nullable, if the value is null or empty, validation will pass. If the value is not null/empty, all rules will be applied.

numeric({String? message}) → FormValidator

Validate that the value is numeric

password({required int strength, String? message}) → FormValidator

Validate that the value is a password

phoneNumberUk({String? message}) → FormValidator

Validate a UK phone number

phoneNumberUs({String? message}) → FormValidator

Validate a US phone number

postcodeUk({String? message}) → FormValidator

Validate that the value is a valid postcode for the UK

regex(String regex, {String? message}) → FormValidator

Validate that the value matches a regex pattern

setAttribute(String? attribute) → void

Sets the attribute name for error messages.

setData(dynamic data) → void

Set the data for the form validator

that(dynamic data, [String? attribute]) → FormValidator

Configures the validator with the value and attribute to validate, then returns this so rules can be chained.

toString() → String

A string representation of this object.

inherited

uppercase({String? message}) → FormValidator

Validate that the value is uppercase

url({String? message}) → FormValidator

Validate a URL

zipcodeUs({String? message}) → FormValidator

Validate that the value is a valid zipcode for the US

Operators

operator ==(Object other) → bool

The equality operator.

inherited