Qt5 Tutorial QtXML - 2020

In this tutorial, we will learn about QtXML.

To include the definitions of the module's classes, use the following directive:

#include <QtXml>

To link against the module, add this line to our qmake .pro file:

QT += xml

Though the QtXML docuemnt says:

The module is not actively maintained anymore.
Please use the QXmlStreamReader and QXmlStreamWriter classes in Qt Core instead.

We still need to understand QtXML to move on to the other topics.

In this example, we will write a XML document.

#include <QtCore>
#include <QtXML>
#include <QDebug>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    // Create a document to write XML
    QDomDocument document;

    // Making the root element
    QDomElement root = document.createElement("Dorms");

    // Adding the root element to the docuemnt
    document.appendChild(root);

    // Writing to a file
    QFile file("C:/Test/myXLM.xml");
    if(!file.open(QIODevice::WriteOnly | QIODevice::Text))
    {
        qDebug() << "Open the file for writing failed";
    }
    else
    {
        QTextStream stream(&file;);
        stream << document.toString();
        file.close();
        qDebug() << "Writing is done";
    }

    return a.exec();
}

First, we need to create a document:

QDomDocument document;

Then, make a root element and attach it to the document:

// Making the root element
QDomElement root = document.createElement("Dorms");

// Adding the root element to the docuemnt
document.appendChild(root);

Then, open a file and start to writng using QTextStream:

QTextStream stream(&file;);
stream << document.toString();

We can open the XML document to see using XML editor:

<?xml version="1.0"?>
<Dorms/>

If we add child elements:

// Adding the root element to the docuemnt
document.appendChild(root);

// Adding more elements
for(int i = 0; i < 5; i++)
{
    QDomElement dorm = document.createElement("Dorm");
    dorm.setAttribute("Name", "Dorm Building " + QString::number(i));
    dorm.setAttribute("ID", QString::number(i));
    root.appendChild(dorm);
}

Open the XML doc:

<Dorms>
 <Dorm ID="0" Name="Dorm Building 0"/>
 <Dorm ID="1" Name="Dorm Building 1"/>
 <Dorm ID="2" Name="Dorm Building 2"/>
 <Dorm ID="3" Name="Dorm Building 3"/>
 <Dorm ID="4" Name="Dorm Building 4"/>
</Dorms>

Now, we want to put rooms to each dorm building:

    document.appendChild(root);

    // Adding more elements
    for(int i = 0; i < 5; i++)
    {
        QDomElement dorm = document.createElement("Dorm");
        dorm.setAttribute("Name", "Dorm Building " + QString::number(i));
        dorm.setAttribute("ID", QString::number(i));
        root.appendChild(dorm);

        // Adding rooms to each dorm building
        for(int j = 0; j < 3; j++)
        {
            QDomElement room = document.createElement("Room");
            room.setAttribute("Name", "Room " + QString::number(j));
            room.setAttribute("ID", QString::number(j));
            dorm.appendChild(room);
        }
    }

Indeed, each Dorm building has rooms now:

<Dorms>
 <Dorm ID="0" Name="Dorm Building 0">
  <Room ID="0" Name="Room 0"/>
  <Room ID="1" Name="Room 1"/>
  <Room ID="2" Name="Room 2"/>
 </Dorm>
 <Dorm ID="1" Name="Dorm Building 1">
  <Room ID="0" Name="Room 0"/>
  <Room ID="1" Name="Room 1"/>
  <Room ID="2" Name="Room 2"/>
 </Dorm>
 <Dorm ID="2" Name="Dorm Building 2">
  <Room ID="0" Name="Room 0"/>
  <Room ID="1" Name="Room 1"/>
  <Room ID="2" Name="Room 2"/>
 </Dorm>
 <Dorm ID="3" Name="Dorm Building 3">
  <Room ID="0" Name="Room 0"/>
  <Room ID="1" Name="Room 1"/>
  <Room ID="2" Name="Room 2"/>
 </Dorm>
 <Dorm ID="4" Name="Dorm Building 4">
  <Room ID="0" Name="Room 0"/>
  <Room ID="1" Name="Room 1"/>
  <Room ID="2" Name="Room 2"/>
 </Dorm>
</Dorms>

Here is the final version of source code, main.cpp.

#include <QtCore>
#include <QtXML>
#include <QDebug>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    // Create a document to write XML
    QDomDocument document;

    // Making the root element
    QDomElement root = document.createElement("Dorms");

    // Adding the root element to the docuemnt
    document.appendChild(root);

     // Adding more elements
     for(int i = 0; i < 5; i++)
     {
         QDomElement dorm = document.createElement("Dorm");
         dorm.setAttribute("Name", "Dorm Building " + QString::number(i));
         dorm.setAttribute("ID", QString::number(i));
         root.appendChild(dorm);

         // Adding rooms to each dorm building
         for(int j = 0; j < 3; j++)
         {
             QDomElement room = document.createElement("Room");
             room.setAttribute("Name", "Room " + QString::number(j));
             room.setAttribute("ID", QString::number(j));
             dorm.appendChild(room);
         }
     }

    // Writing to a file
    QFile file("C:/Test/myXLM.xml");
    if(!file.open(QIODevice::WriteOnly | QIODevice::Text))
    {
        qDebug() << "Open the file for writing failed";
    }
    else
    {
        QTextStream stream(&file;);
        stream << document.toString();
        file.close();
        qDebug() << "Writing is done";
    }

    return a.exec();
}