QDomDocument get element by class

Question

I have several divs in an HTML file with different classes, like this:

<div class='A'>...</div>
<div class='B'>...</div>
<div class='C'>...</div>

I have a Qt (4.7) program where I need to be able to get a certain div out of this based on the class. I need to use QDomDocument in this program. I know from the documentation that that class has a function elementById(), but I can't get that to work with classes, just ids. This isn't a HTML file a made or anything, so I don't have any control over whether it's class or id. Is there a way to do this that I'm missing? Thanks!

Answer 1

It looks like you need something like this along the lines:

main.cpp

#include <QDomDocument>
#include <QDomElement>
#include <QDomNodeList>
#include <QDomAttr>

#include <QFile>
#include <QDebug>

int main()
{
    QDomDocument doc("mydocument");
    QFile file("mydocument.xml");
    if (!file.open(QIODevice::ReadOnly))
        return 1;

    if (!doc.setContent(&file)) {
        file.close();
        return 1;
    }
    file.close();

    QDomNodeList divNodeList = doc.elementsByTagName("div");

    for (int i = 0; i < divNodeList.size(); ++i) {
        QDomElement domElement = divNodeList.at(i).toElement();
        QDomAttr attribute = domElement.attributeNode("class");
        qDebug() << "Attribute value" << attribute.value();
        if (attribute.value() == "A")
            qDebug() << "Found A";
    }

    return 0;
}

Output

g++ -Wall -fPIC -I/usr/include/qt -I/usr/include/qt/QtCore -I/usr/include/qt/QtXml -lQt5Xml -lQt5Core main.cpp && ./a.out

Answer 2

Try getting the div elements first, by doing this:

QDomDocument l_doc;
l_doc.setContent( "here goes your html" );
QDomNodeList l_divs( l_doc.elementsByTagName( "div" ) );

then you can retrieve the attributes values with this:

for ( int i = 0 ; i < l_divs.size() ; ++i ) {
    QDomElement l_div( l_divs.at( i ).toElement() );
    QString l_class( l_div.attribute( "class" ) );
    qDebug() << "class attribute:" << l_class;
}

I suggest you reconsider the use of QDomDocument and try QWebView and QWebElement instead. With these classes you can use CSS selectors, what would make this (and others) tasks much easier.