qValidator function

String? Function(String?) qValidator(List<TextValidationRule> rules, {OnFailureCallBack? onFail, bool useNations = true})

? build and return String Function(String value) ? which triggers the provided validation rules

• how the validation loop works it will loop for each in the rules List if the role is type of optional it wail mark the validation process for ths item as optional which mans in case of any validation fails and the value is null there will be no error but if the validations fails and the value is not null will return the first fail error message

Implementation

String? Function(String?) qValidator(
  List<TextValidationRule> rules, {
  OnFailureCallBack? onFail,
  bool useNations = true,
}) {
  return (String? input) {
    if (input == null) return null;

    /// if the validator loop has any `IsOptional` Rule this will make
    /// this variables = `true`;
    /// we will need to decide later on if the loop has
    /// `IsOptional` rule on it or not
    var isOptional = false;

    /// will contains the first failed rule message
    String? msg;

    for (final rule in rules) {
      /// if any rules contains `IsOptional`
      /// the validator loop will return `TextFiled` value `isEmpty`
      /// and will not consider any faller from any rule
      /// ! else it will work as usual and validated the next rule and return
      ///  only the first failure
      if (rule is IsOptional) isOptional = true;

      /// * call the validate function and
      /// if it return null then the will be no error;
      /// else ir will return the failure message
      /// which will be return as the validation
      ///  error for the entire validation process
      msg = rule.isValid(input)
          ? null
          : (rule.error ?? ValidatorsLocalization.translate(rule));

      /// if the failure message `msg` has value on it
      /// that means some rule has failed
      /// and we return only the first failure
      /// so there is no reason to continue validation the remain rules
      if (msg != null) {
        onFail?.call(input, rules, rule);
        break;
      }
    }

    if (isOptional && isEmpty(input)) return null;

    return msg;
  };
}