(Qt) Qtimer doesn't work. What details have I missed?

Question

I wrote a header xx.h, there are two classes, one is a Qt class "QClass" and another is a generic class "Normal" . And declare an external Normal variable. Normal has a QClass member.
Here is the content of xx.h :

#ifndef XX_H
#define XX_H

#include <QObject>
#include <QTimer>

class QClass : public QObject
{
    Q_OBJECT

public:
    QClass();
    ~QClass();

private:
    QTimer *t;
private slots:
    void func();
};

class Normal
{
    int i;

    QClass q;
};

extern Normal globalN;

#endif

I also wrote a xx.cpp to implement xx.h

#include "xx.h"

QClass::QClass() : t(new QTimer)
{
    connect(t, SIGNAL(timeout()), this, SLOT(func()));
    t->start(1000);
}

QClass::~QClass()
{
    delete t;
}


void QClass::func()
{
    static int n = 0;
    ++n;
}

And here is my main.cpp, here I define globalN. The class Why is my Qt window class, it is declared in why.h . This header is not important, so I didn't post its content.

#include "why.h"
#include "xx.h"
#include <QtWidgets/QApplication>

Normal globalN;

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Why w;
    w.show();
    return a.exec();
}

My idea is that I put globalN in global scope, so when program starts, it constructs globalN, then the timer start to tick.
In order to check these stuff work right or not, I set a breakpoint in QClass::func() , to check if QTimer calls func() , but it doesn't.
I examine the code a long time, but I can't find where I mistake, please tell me. Thank you!!

Answer 1

For your timer to start, you need an event loop. To have an event loop you need to have an active QApplication .

Here, since globalN is global, it is created before your QApplication , so your timer is not started.