Runtime error with tinyXML element access - c++

Question

yester day was my first attempt. I am trying to catch the variable "time" in the following "new.xml" file
<?xml version="1.0" standalone=no>
<main>
<ToDo time="1">
<Item priority="1"> Go to the <bold>Toy store!</bold></Item>
<Item priority="2"> Do bills</Item>
</ToDo>
<ToDo time="2">
<Item priority="1"> Go to the Second<bold>Toy store!</bold></Item>
</ToDo>
</main>
Here is my code
TiXmlDocument doc("new.xml");
TiXmlNode * element=doc.FirstChild("main");
element=element->FirstChild("ToDo");
string temp=static_cast<TiXmlElement *>(element)->Attribute("time");
But I am getting run time errors from the third and fourth lines. Can anybody shed a light on this isssue?

Answer 1

It seems to me that you forgot to load the file. Normally I do something along these lines:
TiXmlDocument doc("document.xml");
bool loadOkay = doc.LoadFile(); // Error checking in case file is missing
if(loadOkay)
{
TiXmlElement *pRoot = doc.RootElement();
TiXmlElement *element = pRoot->FirstChildElement();
while(element)
{
string value = firstChild->Value(); // In your example xml file this gives you ToDo
string attribute = firstChild->Attribute("time"); //Gets you the time variable
element = element->NextSiblingElement();
}
}
else
{
//Error conditions
}
Hope this helps

Answer 2

#include "tinyXml/tinyxml.h"
const char MY_XML[] = "<?xml version='1.0' standalone=no><main> <ToDo time='1'> <Item priority='1'> Go to the <bold>Toy store!</bold></Item> <Item priority='2'> Do bills</Item> </ToDo> <ToDo time='2'> <Item priority='1'> Go to the Second<bold>Toy store!</bold></Item> </ToDo></main>";
void main()
{
TiXmlDocument doc;
TiXmlHandle docHandle(&doc);
const char * const the_xml = MY_XML;
doc.Parse(MY_XML);
TiXmlElement* xElement = NULL;
xElement = docHandle.FirstChild("main").FirstChild("ToDo").ToElement();
int element_time = -1;
while(xElement)
{
if(xElement->QueryIntAttribute("time", (int*)&element_time) != TIXML_SUCCESS)
throw;
xElement = xElement->NextSiblingElement();
}
}
That's how it works. Compiled & tested.
As you can see your tries to make it extra-safe code cost you with an exceotion at your third line (of the question), and without testing I can bet it's a "pointing-to-null" exception.
Just load it my style, as TinyXml's docs say as well: "docHandle.FirstChild("main").FirstChild("ToDo").ToElement();".
Hope it helps you understand, let me know if it's not clear. I accept visa (:

Answer 3

Is it just me or the the pugixml version looks much better?
#include <iostream>
#include "pugixml.hpp"
using namespace std;
using namespace pugi;
int main()
{
xml_document doc;
if (!doc.load_file("new.xml"))
{
cerr << "Could not load xml";
return 1;
}
xml_node element = doc.child("main");
element = element.child("ToDo");
cout << "Time: " << element.attribute("time") << endl;
}
Also new.xml had an error, instead of:
<?xml version="1.0" standalone=no>
should be
<?xml version="1.0" standalone="no"?>
Compilation was just a matter of cl test.cpp pugixml.cpp