lengthValidator function
Validates the length of the input value based on minimum and maximum constraints.
Implementation
String? lengthValidator(String value, {int? min, int? max}) {
if (min != null && value.length < min) {
return 'The value must be at least $min characters.';
}
if (max != null && value.length > max) {
return 'The value must be at most $max characters.';
}
return null;
}