seeing undefined reference to `vtable for CollidingMice'

Question

I'm modifying a Qt example 'collidingmice' which comes with the Qt code.
In the original source, the QApplication contains QView and QScene, but I made a class CollidingMice containing the QView and QScene to kill the view and scene using keyboard input. I want to send the keyboard input to CollidingMice class. I read 4 or 5 questions in stack overflow about 'undefined reference to vtable for..' but could not find the case that fits me. I checked that
1. there is no virtual function in the parent classes that is not defined.
2. I tried adding definition of destructor ~CollidingMices() {}
3. and I'm 99% sure there is no undefined member function in the CollidingMice code below.

#include "mouse.h"

#include <QtGui>


#include <math.h>

static const int MouseCount = 7;
class CollidingMice : public QMainWindow
{
        Q_OBJECT

        private:
                QGraphicsView *view;
                QGraphicsScene scene;
                QTimer *timer;

        public:
                CollidingMice(QWidget *parent = 0): QMainWindow(parent) {
                        scene.setSceneRect(-300, -300, 600, 600);
                        scene.setItemIndexMethod(QGraphicsScene::NoIndex);
                        for (int i = 0; i < MouseCount; ++i) {
                                Mouse *mouse = new Mouse;
                                mouse->setPos(::sin((i * 6.28) / MouseCount) * 200,
                                                ::cos((i * 6.28) / MouseCount) * 200);
                                scene.addItem(mouse);
                        }
                        view = new QGraphicsView(this);
                        view->setRenderHint(QPainter::Antialiasing);
                        view->setBackgroundBrush(QPixmap(":/images/cheese.jpg"));
                        view->setCacheMode(QGraphicsView::CacheBackground);
                        view->setViewportUpdateMode(QGraphicsView::BoundingRectViewportUpdate);
                        view->setDragMode(QGraphicsView::ScrollHandDrag);
                        view->setWindowTitle(QT_TRANSLATE_NOOP(QGraphicsView, "Colliding Mice"));
#if defined(Q_WS_S60) || defined(Q_WS_MAEMO_5) || defined(Q_WS_SIMULATOR)
                        view->showMaximized();
#else
                        view->resize(600, 450);
                        view->move(30,30);
                        view->show();
#endif
                        timer = new QTimer;
                        QObject::connect(timer, SIGNAL(timeout()), &scene, SLOT(advance()));
                        timer->start(1000 / 33);
                }

        private:
                void keyPressEvent(QKeyEvent *event);
};

void  CollidingMice::keyPressEvent(QKeyEvent *event)
{
                if (event->key() == Qt::Key_q) {
                                close();
                }
}

int collidingmice_main(int argc, char **argv)
{
                QApplication app(argc, argv);
                qsrand(QTime(0,0,0).secsTo(QTime::currentTime()));

                CollidingMice w;

                return app.exec();
}

ADD and EDIT : After deleting the QOBJECT above as svlasov told me to, and after fixing the constructor as below (see the setScene..my colleage suggested me.)

               view = new QGraphicsView(this);
                view->resize(600,500);
                view->setScene(&scene);
                view->setRenderHint(QPainter::Antialiasing);

I could compile it and execute it.

Answer 1

If you use Q_OBJECT in class definition you have to extract the class into separate header file.

If you don't declare signals and slots in CollidingMice class, just remove Q_OBJECT and it will compile.

UPDATE

As @KubaOber commented, you can simply include to the end of your file.cpp file:

#include "file.moc"

and qmake will do all the job.