Find a specific node in a XML document with TinyXML - c++

Question

I want to parse some data from an xml file with TinyXML.
Here's my text.xml file content:
<?xml version="1.0" encoding="iso-8859-1"?>
<toto>
<tutu>
<tata>
<user name="toto" pass="13" indice="1"/>
<user name="tata" pass="142" indice="2"/>
<user name="titi" pass="azerty" indice="1"/>
</tata>
</tutu>
</toto>
I want to access to the first element 'user'. The way to do this is the following :
TiXmlDocument doc("test.xml");
if (doc.LoadFile())
{
TiXmlNode *elem = doc.FirstChildElement()->FirstChildElement()->FirstChildElement()->FirstChildElement();
std::cout << elem->Value() << std::endl;
}
In output : user.
But the code is pretty ugly and not generic. I tried the code below to simulate the same behaviour than the code above but it doesn't work and an error occured.
TiXmlElement *getElementByName(TiXmlDocument &doc, std::string const &elemt_value)
{
TiXmlElement *elem = doc.FirstChildElement(); //Tree root
while (elem)
{
if (!std::string(elem->Value()).compare(elemt_value))
return (elem);
elem = elem->NextSiblingElement();
}
return (NULL);
}
Maybe I missed a special function in the library which can do this work (a getElementByName function). I just want to get a pointer to the element where the value is the one I'm looking for. Does anyone can help me? Thanks in advance for your help.

Answer 1

Try this
TiXmlElement * getElementByName(TiXmlDocument & doc, std::string const & elemt_value) {
TiXmlElement * elem = doc.RootElement(); //Tree root
while (elem) {
if (!std::string(elem - > Value()).compare(elemt_value)) return (elem);
/*elem = elem->NextSiblingElement();*/
if (elem - > FirstChildElement()) {
elem = elem - > FirstChildElement();
} else if (elem - > NextSiblingElement()) {
elem = elem - > NextSiblingElement();
} else {
while (!elem - > Parent() - > NextSiblingElement()) {
if (elem - > Parent() - > ToElement() == doc.RootElement()) {
return NULL;
}
elem = elem - > Parent() - > NextSiblingElement();
}
}
}
return (NULL);
}

Answer 2

Adi's answer didn't work when i just copy pasted it into my code,
but i modified it and now it works fine for me.
since i made quite a lot of changes i thought i should post my final code here.
void parseXML(tinyxml2::XMLDocument& xXmlDocument, std::string sSearchString, std::function<void(tinyxml2::XMLNode*)> fFoundSomeElement)
{
if ( xXmlDocument.ErrorID() != tinyxml2::XML_SUCCESS )
{
// XML file is not ok ... we throw some exception
throw DataReceiverException( "XML file parsing failed" );
} // if
//ispired by http://stackoverflow.com/questions/11921463/find-a-specific-node-in-a-xml-document-with-tinyxml
tinyxml2::XMLNode * xElem = xXmlDocument.FirstChild();
while(xElem)
{
if (xElem->Value() && !std::string(xElem->Value()).compare(sSearchString))
{
fFoundSomeElement(xElem);
}
/*
* We move through the XML tree following these rules (basically in-order tree walk):
*
* (1) if there is one or more child element(s) visit the first one
* else
* (2) if there is one or more next sibling element(s) visit the first one
* else
* (3) move to the parent until there is one or more next sibling elements
* (4) if we reach the end break the loop
*/
if (xElem->FirstChildElement()) //(1)
xElem = xElem->FirstChildElement();
else if (xElem->NextSiblingElement()) //(2)
xElem = xElem->NextSiblingElement();
else
{
while(xElem->Parent() && !xElem->Parent()->NextSiblingElement()) //(3)
xElem = xElem->Parent();
if(xElem->Parent() && xElem->Parent()->NextSiblingElement())
xElem = xElem->Parent()->NextSiblingElement();
else //(4)
break;
}//else
}//while
}
(for completeness) example how to call the function:
tinyxml2::XMLDocument xXmlDocument;
xXmlDocument.Parse(sXmlDocument.c_str());
parseXML(xXmlDocument, "user",[](tinyxml2::XMLNode* xElem)
{
int iPass;
xElem->QueryIntAttribute( "pass", &iPass );
std::cout << iPass << "\n";
});

Answer 3

You can also iterate through your XML elements one-by-one by using recursive function combined with lamda-function as a handler.
//
// This function will iterate through your XML tree and call the 'parseElement' function for each found element.
//
void RecursiveXMLParse(TiXmlElement* element, std::function<void(TiXmlElement*)>& parseElement)
{
if (element != nullptr)
{
parseElement(element);
auto child = element->FirstChildElement();
if (child != nullptr)
{
RecursiveXMLParse(child, parseElement);
}
for (auto sibling = element->NextSiblingElement(); sibling != nullptr; sibling = sibling->NextSiblingElement())
{
RecursiveXMLParse(sibling, parseElement);
}
}
}
Usage: Just pass the XML root element, and your data handler lambda function to the recursive Parser-function.
int main()
{
//
// Define your data handler labmda
//
std::function<void(TiXmlElement*)>parseElement = [&](TiXmlElement* e) -> void
{
if (std::string(elem->Value()).compare("user"))
{
// Parse your user data
}
};
// Pass the root element along with the above defined lambda to the recursive function
RecursiveXMLParse(doc.RootElement(), parseElement);
return 0;
}

Answer 4

XMLElement *getElementByName(XMLDocument &ele, std::string const &elemt_value)
{
XMLElement *elem = ele.FirstChildElement(); //Tree root
while (elem)
{
if (!std::string(elem->Value()).compare(elemt_value))
return elem;
if (elem->FirstChildElement())
{
elem = elem->FirstChildElement();
}
else if (elem->NextSiblingElement())
{
elem = elem->NextSiblingElement();
}
else
{
if (elem->Parent()->ToElement()->NextSiblingElement())
{
elem = elem->Parent()->ToElement()->NextSiblingElement();
}
else if (elem->Parent()->ToElement()->FirstChildElement()
&& strcmp(elem->Name(), elem->Parent()->ToElement()->FirstChildElement()->Name()))
{
elem = elem->Parent()->ToElement()->FirstChildElement();
}
else {
break;
}
}
}
return NULL;
}
// A small tweak in the above given solution