/**
  * @param Request $request
  *
  * @return boolean|null
  */
 private function validateGender(Request $request)
 {
     $gender = self::$validator->isInteger('gender');
     $result = $gender->isRequired()->isPositive()->isBetween(0, 2, true)->validate($request->gender);
     $this->isValid = $this->isValid && $result;
     $this->errors = array_merge($this->errors, $gender->getErrors());
 }