QT and C++: can't call function outside main() function - c++

Question

I would like to know how to call the function Do_Download() from the SocketTest class outisde the main() function.
The first cTest.Do_Download() does work, but when I call the test() function, the csTest.Do_Download() does not work.
So it looks like I can only acces SocketTest from inside the main() function, and not from any other function.
Does somebody know how this can be solved?
Thanks!
main.cpp:
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
SocketTest cTest;
cTest.Do_Download();
return a.exec();
}
void test()
{
qDebug() << "test main functie";
SocketTest csTest;
csTest.Do_Download();
}
SocketTest.h:
#ifndef SOCKETTEST_H
#define SOCKETTEST_H
#include <QObject>
#include <QTcpSocket>
#include <QDebug>
#include <QHttp>
#include <QFile>
#include <QString>
class SocketTest : public QObject
{
Q_OBJECT
public:
explicit SocketTest(QObject *parent = 0);
void Do_Download();
signals:
public slots:
void stateChanged ( int state );
void responseHeaderReceived ( const QHttpResponseHeader & resp );
void requestFinished ( int id, bool error );
private:
QTcpSocket *socket;
QHttp *http;
QHttp *http2;
};
#endif // SOCKETTEST_H

Answer 1

If your DoDownload function is doing anything asynchronously (likely, when dealing with the Qt networking classes), the SocketTest you are creating in test() is being destroyed before it can act on any return value.
It works in main() because the event loop starts and the SocketTest instance hangs around.