The ValidationResult class contains the results of a validation.

class ValidationResult {
 
 /**
  * Pass true if there was a validation error.
  */
 final bool isError;
 
 /**
  * Validation error message.
  */
 final String message;
 
 /**
  * Create new instance of [ValidationResult]. You might specify [isError] if
  * validation process finished with error and pass throug result [message].
  */
 ValidationResult(this.isError, this.message);
 
 /**
  * Use [message] content to convert that instance to String.
  */
 String toString() {
   return message == null ? "" : message;
 }
}