problem running GUI thread and worker thread concurrently

[prkhr4u]

I am using 2 threads: GUI thread and 1 worker thread(grabthread),but i am not able to run them concurrently.
My main() function is like this :

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow win;
    win.show();
    GrabThread thread;
         thread.start();
         qDebug() << "hello from GUI thread " << a.thread()->currentThreadId();
         thread.wait();  // do not exit before the thread is completed!
    return a.exec();
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow win;
    win.show();
    GrabThread thread;
         thread.start();
         qDebug() << "hello from GUI thread " << a.thread()->currentThreadId();
         thread.wait();  // do not exit before the thread is completed!
    return a.exec();
}

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and grabthread.h like this:

class GrabThread : public QThread
{
    Q_OBJECT
     private:
      void run();
};

class GrabThread : public QThread
{
    Q_OBJECT
     private:
      void run();
};

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What is happening is that My GUI pops up only after grabthread has been fully executed and exits.
I want my GUI and grabthread to start simultaneously so that i can use multithreading.