xml文件操作

一.写入

 // 创建文件夹
    QDir dir;
    if (!dir.mkpath(path))
    {
        qCritical() << "Error: cannot create folder.";
        return ;
    }
    xml_document doc;
    xml_node root = doc.append_child("map");
    root.append_attribute("generator")="map editor";
    root.append_attribute("upload")="true";
    root.append_attribute("version")="0.6";
    for (const auto& pair : points)
    {
        xml_node node = roadToPointsNode(pair.second, root);
    }
    for (const auto& pair : lines)
    {
        xml_node node = roadToLinesNode(pair.second, root);
    }
    for (const auto& pair : curves)
    {
        xml_node node = roadToLinesNode(pair.second, root);
    }
    doc.save_file((path+"/road_map.xml").toStdString().c_str());