RapidXML loading xml files

Question

I cannot return the loadings from the xml. Here is the code:

RapidXML xml loader

vector<char*> ParseFanbeamGeometry(char* fileName)
{
    xml_document<> doc;
    xml_node<> * root_node;
    // Read the xml file into a vector
    ifstream theFile (fileName);
    vector<char> buffer((istreambuf_iterator<char>(theFile)), istreambuf_iterator<char>());
    buffer.push_back('\0');
    // Parse the buffer using the xml file parsing library into doc 
    doc.parse<0>(&buffer[0]);
    // Find our root node
    root_node = doc.first_node("FanbeamGeometrySettings");

    vector<char*> fambeamGeometry;
    // Iterate over the fangeometry
    for (xml_node<> * fanGeometry_node = root_node->first_node("FanGeometry"); fanGeometry_node; fanGeometry_node = fanGeometry_node->next_sibling())
    {      
        try
        {
            fambeamGeometry.push_back(fanGeometry_node->first_attribute("geometry")->value());
            fambeamGeometry.push_back(fanGeometry_node->first_attribute("D")->value());
        }
        catch (exception &e)
        {
            e.what();
        }
    }

    return fambeamGeometry;

}

main function

int _tmain(int argc, _TCHAR* argv[])
{
    char* fangeofile = "D:\\Projects\\fanbeam\\tools\\rapidxml-1.13\\GeometrySettings.xml";

    vector<char*> fambeamGeometry = ParseFanbeamGeometry(fangeofile);

    float D = atof(fambeamGeometry[1])*N;

    getchar();
    return 0;
}

xml file

<?xml version="1.0"?>
<FanbeamGeometrySettings>
  <FanGeometry geometry="EquiDistance" D="2"/>
</FanbeamGeometrySettings>

The fambeamGeometry properly loads "EquiDistance" and "2", but when it is returned from ParseFanbeamGeometry() to main, the value becomes some weird values, like -18 and -2.

Any suggestions? I have no idea why. How to let the xml loader return what it loads? Thanks.

Answer 1

Use vector<std::string> instead of

vector<char*> 

then, use string.c_str() to convert string to

char*

Answer 2

Your function ParseFanbeamGeometry is returning a vector of pointers, but the data that they point to will be invalid once buffer gets destructed as the function returns.

The correct approach, as you've realized is to pass back std::strings instead. That's the idiomatic approach in C++ anyway.

vector<std::string> ParseFanbeamGeometry(const std::string &fileName)