Replacing XML element value using QDomDocument

[mj]

Hi,
Im using QDomDocument for xml file.

My xml file has the following data,

<?xml version="1.0"?>
<config>
<dbus>
       <gas_value>2</gas_value>
 </dbus>
</config>

<?xml version="1.0"?>
<config>
<dbus>
       <gas_value>2</gas_value>
 </dbus>
</config>

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I want to replace <gas_value>2</gas_value> with <gas_value>100</gas_value>

Im using following code to replace it

QFile *file = new QFile("dbus_write.xml");
 
    if (!file->open(QIODevice::ReadWrite | QIODevice::Text))
    {
        qDebug() << "unable to open xml file";
        return;
    }
 
    QDomDocument doc("dbus_write");
    doc.setContent(file);
 
    QDomElement root = doc.firstChildElement("config");
    QDomElement parent = root.firstChildElement("dbus");
    QDomElement gasvalue = parent.firstChildElement("gas_value");
    parent.firstChildElement("gas_value").firstChild().setNodeValue("100");
    QTextStream stream(file);
    gasvalue.save(stream, 4);
    file->close();

QFile *file = new QFile("dbus_write.xml");
    
    if (!file->open(QIODevice::ReadWrite | QIODevice::Text))
    {
        qDebug() << "unable to open xml file";
        return;
    }

    QDomDocument doc("dbus_write");
    doc.setContent(file);

    QDomElement root = doc.firstChildElement("config");
    QDomElement parent = root.firstChildElement("dbus");
    QDomElement gasvalue = parent.firstChildElement("gas_value");
    parent.firstChildElement("gas_value").firstChild().setNodeValue("100");
    QTextStream stream(file);
    gasvalue.save(stream, 4);
    file->close();

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but this code doesn't replaces the tag <gas_value>2</gas_value> , instead it creates another tag <gas_value>100</gas_value>
and produces following xml file

<?xml version="1.0"?>
<config>
<dbus>
       <gas_value>2</gas_value>
 </dbus>
</config>
 
      <gas_value>100</gas_value>

<?xml version="1.0"?>
<config>
<dbus>
       <gas_value>2</gas_value>
 </dbus>
</config>
      
      <gas_value>100</gas_value>

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I tried using replaceChild() method, but results in same output.

Any thoughts?
thanks.

[mj]

solved.. below code works fine for me..

QFile *file = new QFile("dbus_write.xml");

if (!file->open(QIODevice::ReadWrite | QIODevice::Text))
{
qDebug() << "unable to open xml file";
return;
}
QByteArray xmlData(file->readAll());
QDomDocument doc("dbus_write");
doc.setContent(xmlData);

QDomElement root = doc.firstChildElement("config");
QDomElement parent = root.firstChildElement("dbus");
QDomElement gasvalue = parent.firstChildElement("gas_value");
parent.firstChildElement("gas_value").firstChild() .setNodeValue("100");
file->resize(0);
QTextStream stream(file);
stream.setDevice(file);
doc.save(stream, 4);
file->close();

[ChrisW67]

You should address the memory leak surrounding the (unnecessary) use of the heap for your QFile instance.