Strange xml behaviour when opening the file.

[cbarmpar]

Hi all,

I am experiencing a strange behaviour when i am trying to read an xml file.
I just want to print a message when the startofdocument is found.

the header file:

#ifndef KENTRIKO_H
#define KENTRIKO_H
#include <QtGui>
#include <QApplication> 
#include <QtCore> 
#include "ui_kentriko.h"
 
class kentriko : public QMainWindow
{
    Q_OBJECT
 
public:
    kentriko(QWidget *parent = 0);
    ~kentriko();
public slots:
void anigma_arxiou();
void diabase();
 
private:
    Ui::kentrikoClass ui;
    QXmlStreamReader ena;
};
 
#endif // KENTRIKO_H

#ifndef KENTRIKO_H
#define KENTRIKO_H
#include <QtGui>
#include <QApplication> 
#include <QtCore> 
#include "ui_kentriko.h"

class kentriko : public QMainWindow
{
    Q_OBJECT

public:
    kentriko(QWidget *parent = 0);
    ~kentriko();
public slots:
void anigma_arxiou();
void diabase();

private:
    Ui::kentrikoClass ui;
    QXmlStreamReader ena;
};

#endif // KENTRIKO_H

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the implementation

kentriko::kentriko(QWidget *parent)
    : QMainWindow(parent)
{
	ui.setupUi(this);
	connect(ui.anigma,SIGNAL(clicked()),this,SLOT(anigma_arxiou()));
	connect(ui.diabase,SIGNAL(clicked()),this,SLOT(diabase()));
}
 
kentriko::~kentriko()
{
 
}
void kentriko::anigma_arxiou(){
	QString fileName =
	             QFileDialog::getOpenFileName(this, tr("anigma arxiou"),
	                                          QDir::currentPath(),tr("arxia tipou  (*.xml)"));
	     if (fileName.isEmpty())
	         return;
	 QFile file(fileName);
	 ui.textBrowser->append(fileName);
	file.open(QFile::ReadOnly | QFile::Text);
	 ena.setDevice(&file);
}
 
void kentriko::diabase(){
ena.readNext();
if (ena.isStartDocument()){
	ui.textBrowser->append("start of document found");
};
//ena.readNext();
 
}

kentriko::kentriko(QWidget *parent)
    : QMainWindow(parent)
{
	ui.setupUi(this);
	connect(ui.anigma,SIGNAL(clicked()),this,SLOT(anigma_arxiou()));
	connect(ui.diabase,SIGNAL(clicked()),this,SLOT(diabase()));
}

kentriko::~kentriko()
{

}
void kentriko::anigma_arxiou(){
	QString fileName =
	             QFileDialog::getOpenFileName(this, tr("anigma arxiou"),
	                                          QDir::currentPath(),tr("arxia tipou  (*.xml)"));
	     if (fileName.isEmpty())
	         return;
	 QFile file(fileName);
	 ui.textBrowser->append(fileName);
	file.open(QFile::ReadOnly | QFile::Text);
	 ena.setDevice(&file);
}

void kentriko::diabase(){
ena.readNext();
if (ena.isStartDocument()){
	ui.textBrowser->append("start of document found");
};
//ena.readNext();
    
}

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:

and the xml that I am trying to read:

<adbook>
 <contact email="kal@goteborg.se" phone="+46(0)31 123 4567" name="Kal" />
 <contact email="ada@goteborg.se" phone="+46(0)31 765 1234" name="Ada" />
</adbook>

<adbook>
 <contact email="kal@goteborg.se" phone="+46(0)31 123 4567" name="Kal" />
 <contact email="ada@goteborg.se" phone="+46(0)31 765 1234" name="Ada" />
</adbook>

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when the diabase function is called my program crashes.

Any idea what might causing this?

Many thanks in advance.

[jacek]

...
QFile file(fileName);
...
ena.setDevice(&file);
}

You pass a pointer to an object created on a stack to setDevice(). When the function returns, "file" gets destroyed.

[cbarmpar]

many thanks for the reply
I don't understand what should i change!
The error occurs when i try to execute the readnext() command.

regards.

[jacek]

Create "file" on the heap or make it a member variable, so that it doesn't go out of scope.

[cbarmpar]

Many thanks for your help.

I have just found it as well.

what do you mean change it in the heap?

Regards.

[jacek]

what do you mean change it in the heap?

The heap is a data structure that is used to manage all dynamically allocated memory. Everything you create with new operator is created on the heap.