onValidate abstract method

String? onValidate(
  1. T? value,
  2. String translator(
    1. String, {
    2. List<String>? params,
    })
)

onValidate is used to validate the given input by the user.

Implementation

String? onValidate(
  T? value,
  String Function(String, {List<String>? params}) translator,
);