protected function isSame(string $key, string $field) : bool
    {
        $other = $this->param[$key];

        if (isset($other) && $field === $other) {
            return true;
        }

        $this->errors[$field.self::ERROR] = $this->convertToFieldName($field).' value must be same as '.
            $this->convertToFieldName($key).'.';

        return false;
    }