Confusion regarding insertion of QDomElement

[WilliamU]

Hello all,

I have an XML file that resembles this :
@<?xml version='1.0' encoding='utf-8'?>
<outputs>
<results>
<data />
<data />
<... />
</results>
<results>
<data />
<data />
<... />
</results>
</outputs>
@

And I want to insert a new set of results:
@
<results>
<data />
<data />
<... />
</results>
@

However, regardless of how I attempt to do this using insertBefore(...) or insertAfter(...) the new QDomElement is never inserted in the correct place, i.e. inside the <outputs> element, either before or after the existing <results> elements.

I have tried various combinations of insertBefore / After on first / lastChild and first and Last ChildElement but none of these insert the <results> in the correct position, and it always ends up outside of the <outputs> or before the xml decl!

Can someone please help me out here. I'm beginning to think I shouldn't have got up this morning!

[giesbert]

Hi,

oit could help if you post some code that you do, the best would be to give some test program that is completly compilable...

[WilliamU]

Hi Gerolf,

I have attached a working! sample as suggested, so here is the .pro file.
@
QT += core xml
QT -= gui
TARGET = xmltest
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
SOURCES += main.cpp
@

and this is this source:
@
int main(int argc, char *argv[])
{
QString period("period"), xmlfile("./results.xml") ;
QDomDocument * m_Doc = new QDomDocument() ;
QFile * input = new QFile(xmlfile) ;
if (input->exists())
{
if (input->open(QFile::ReadOnly | QFile::Text))
{
if (m_Doc->setContent(input))
qDebug() << "Content Set" ;
else
qDebug() << "Unable set content" ;
}
else
{
qDebug() << "Unable to open file!" ;
}
input->close();
}
else
{
m_Doc->appendChild(m_Doc->createProcessingInstruction("xml", "version='1.0' encoding='utf-8'")) ;
m_Doc->appendChild(m_Doc->createElement("output")) ;
}
QDomElement e = m_Doc->createElement("results") ;
QStringList attribs = QStringList() << "Col_1" << "Col_2" << "Col_3" ;
for (int row = 0; row < 4; row++)
{
QDomElement data = m_Doc->createElement("data") ;
data.setAttribute(period, row + 1) ;
for (int a = 0; a < attribs.size(); a++)
{
data.setAttribute(attribs.at(a), QString::number(rand(), 'f', 3)) ;
}
e.appendChild(data) ;
}
// This is the line I have a problem with.
m_Doc->insertBefore(e, m_Doc->firstChild()) ;
QFile outFile(xmlfile) ;
if(outFile.open( QIODevice::WriteOnly | QIODevice::Text ))
{
QTextStream txtStream(&outFile;) ;
m_Doc->save(txtStream, 4);
}
outFile.close();
qDebug() << "Done." ;
std::cin.get() ;
}
@

Thanks.

[KA51O]

You are only inserting after or before the root node (m_Doc) you need to get the element you want to insert before or after and then insert. This way everything should work as desired.

[WilliamU]

Hi KA51O this makes sense, so thank you, so I replaced line 39 with this
@m_Doc->elementsByTagName("output").at(0).appendChild(e) ;@
The structure of the document is now correct and survives re-runs, but I am sure this is not the correct way (in C++ code) to do this. Can anyone clarify please?