validator method
A function that must return a validation error if the provided
value is invalid and null otherwise.
Implementation
@override
PasswordError? validator(String value) {
if (value.trim().isEmpty) return PasswordError.empty;
if (value.length < minLength) return PasswordError.tooShort;
if (requireUppercase && !_uppercase.hasMatch(value)) {
return PasswordError.missingUppercase;
}
if (requireLowercase && !_lowercase.hasMatch(value)) {
return PasswordError.missingLowercase;
}
if (requireNumber && !_number.hasMatch(value)) {
return PasswordError.missingNumber;
}
if (requireSpecialChar && !_specialChar.hasMatch(value)) {
return PasswordError.missingSpecialChar;
}
return null;
}