Serializing class in QDataStream - c++

Question

I am trying to save 3 QVector<QPoint> and an int with QDataStream.
I overloaded the operator<<(), but if I try to save something, nothing appears in the file.
I checked if the QVector is empty, but it wasn't.
So here is the CloudData class with the operator<< and save() function:
CloudData.h
#include <QDataStream>
#include <QVector>
#include <QPoint>
class CloudData
{
public:
CloudData();
QVector<QPoint> getPolyVector() const;
QVector<QPoint> getPathPointVector() const;
QVector<QPoint> getSupPointVector() const;
int getRandSeed() const;
bool save(QString);
friend QDataStream& operator <<(QDataStream &dataStream, const CloudData &cd)
{
dataStream << cd.getPolyVector() << cd.getPathPointVector()
<< cd.getSupPointVector() << cd.getRandSeed();
return dataStream;
}
private:
QVector<QPoint> m_polyVector;
QVector<QPoint> m_pathPointVector;
QVector<QPoint> m_supPointVector;
int m_randSeed;
};
CloudData.cpp
#include "clouddata.h"
#include <QFile>
CloudData::CloudData()
{
}
void CloudData::setPolyVector(QVector<QPoint> pVec)
{
m_polyVector = pVec;
}
void CloudData::setPathPointVector(QVector<QPoint> ppVec)
{
m_pathPointVector = ppVec;
}
void CloudData::setSuppPointVector(QVector<QPoint> spVec)
{
m_supPointVector = spVec;
}
void CloudData::setRandSeed(int randSeed)
{
m_randSeed = randSeed;
}
bool CloudData::save(QString filename)
{
QFile file(filename);
if(!file.open(QIODevice::WriteOnly))
return false;
QDataStream out(&file);
out.setVersion(QDataStream::Qt_4_8);
out << this;
file.close();
return true;
}
And in the end, here is the function, which calls save():
void CloudWidget::saveCloudData()
{
QString filename = QFileDialog::getSaveFileName(this,tr("Save cloud clutter data"),
"/Users/Admin/Downloads/", "Cloud Clutter Data (*.ccd)");
m_cloudData.setPolyVector(m_polygon);
m_cloudData.setPathPointVector(m_pathPointVector);
m_cloudData.setSuppPointVector(m_supPointVector);
m_cloudData.save(filename);
}

Answer 1

I believe the line:
out << this;
in the save() method should be:
out << *this;
The << operator works on a reference to the class, not a pointer to the class.
The following test code illustrates this:
#include <QFile>
#include <QTextStream>
#include <QDebug>
class StreamTest
{
public:
StreamTest() { var1 = "var1"; var2 = "var2"; }
QString var1;
QString var2;
friend QTextStream& operator <<(QTextStream &textStream, const StreamTest &st)
{
textStream << st.var1 << st.var2;
return textStream;
}
void save(void)
{
QString str_1;
QTextStream text_stream_1(&str_1);
text_stream_1 << this;
qDebug() << str_1;
QString str_2;
QTextStream text_stream_2(&str_2);
text_stream_2 << *this;
qDebug() << str_2;
}
};
int main(int argc, char *argv[])
{
StreamTest st;
st.save();
}
Running the code generates the output:
"0x7fff18070c10"
"var1var2"
this prints the pointer value while *this prints the desired output.