call method

@override String? call(String attribute, String value)

Validates whether a value is within the specified list of items.

This method checks if the input value is included in the provided items list. If the value is not found within the list, an error message is generated using the buildMessage method.

Parameters:

• attribute: The identifier of the form attribute being validated.
• value: The value to be validated.

Returns: A validation error message if the value is not within the specified items list, or null if the value is valid.

Implementation

@override
String? call(String attribute, String value) {
  if (value.isNotEmpty) {
    if (!items.contains(value)) {
      return buildMessage(attribute, value, onExtra: (message) {
        message = message.replaceAll(':items', items.toString());
        return message;
      });
    }
  }
  return null;
}