Update XML file in QT

Question

I have Xml file

<root rootname="RName" otherstuff="temp">
     <somechild childname="CName" otherstuff="temp">
     </somechild>
</root>

in the above XML how can I update RName to RN and CName to CN using QT. I am using QDomDocument but not able to do required thing.

Answer 1

It would help if you share information how you are using QDomDocument and which part exactly is tricky. But here how it goes in general:

• file is being read from a file system;

• file is being parsed into QDomDocument;

• content of document is being modified;

• data is being saved back to the file.

In the Qt code:

// Open file
QDomDocument doc("mydocument");
QFile file("mydocument.xml");
if (!file.open(QIODevice::ReadOnly)) {
    qError("Cannot open the file");
    return;
}
// Parse file
if (!doc.setContent(&file)) {
   qError("Cannot parse the content");
   file.close();
   return;
}
file.close();

// Modify content
QDomNodeList roots = elementsByTagName("root");
if (roots.size() < 1) {
   qError("Cannot find root");
   return;
}
QDomElement root = roots.at(0).toElement();
root.setAttribute("rootname", "RN");
// Then do the same thing for somechild
...

// Save content back to the file
if (!file.open(QIODevice::Truncate | QIODevice::WriteOnly)) {
    qError("Basically, now we lost content of a file");
    return;
}
QByteArray xml = doc.toByteArray();
file.write(xml);
file.close();

Note, in real life applications you will want to save data to another file, ensure save was successful and then replace original file with a copy.