C++ (Cpp) optional::data示例

void url::
rebuild(const boost::string_ref &scheme,
        const boost::optional<boost::string_ref> &host,
        const boost::optional<uint16_t> &port,
        const boost::optional<boost::string_ref> &path,
        const boost::optional<boost::string_ref> &query,
        const boost::optional<boost::string_ref> &fragment,
        const boost::optional<boost::string_ref> &user_info)
{
    std::string str;

    str.append(scheme.data(), scheme.size());
    if (has_authority()) {
        str.append("://");

        if (user_info) {
            str.append(user_info->data(), user_info->size());
            str.append("@");
        }

        str.append(host->data(), host->size());

        if (port) {
            str.append(":");
            str.append(std::to_string(*port));
        }
    }
    else {
        str.append(":");
    }

    if (path) {
        str.append(path->data(), path->size());
    }

    if (query) {
        str.append("?");
        str.append(query->data(), query->size());
    }

    if (fragment) {
        str.append("#");
        str.append(fragment->data(), fragment->size());
    }

    url new_url { std::move(str) };
    swap(new_url);
}