undefined reference to 'vtable ...'

I don't understand this error:

Code:

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Undefined reference to 'vtable for Spaceship'   Spaceship.cpp  9
Undefined reference to 'vtable for Spaceship'   Spaceship.cpp  9
collect2: ld returned 1 exit status

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spaceship.h:

Code:

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#ifndef SPACESHIP_H
#define SPACESHIP_H
 
#include <QGraphicsItem>
#include <QObject>
 
class Spaceship : public QGraphicsItem
{
 
public:
    Spaceship();
 
    QRectF boundingRect() const;
    QPainterPath shape() const;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
 
protected:
    void advance(int step);
 
private:
    qreal angle;
    qreal speed;
    QColor color;
};
 
#endif // SPACESHIP_H

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spaceship.cpp:

Code:

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#include "spaceship.h"
#include <QGraphicsScene>
#include <QPainter>
#include <QStyleOption>
#include <QObject>
#include <math.h>
 
Spaceship::Spaceship()
{
    setRotation(0);
}
 
void Spaceship::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
{
    //Draw the Spaceship
    painter->setBrush(Qt::black);
    painter->drawRect(10, 10, 20, 20);
}
 
void Spaceship::advance(int step)
{
    if (!step)
        return;
 
    angle = 0;
    speed += 1;
    setPos(mapToParent(0, -(3 + speed) *3));
}

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main.cpp:

Code:

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#include "spaceship.h"
#include <QtGui>
#include <math.h>
#include <QObject>
 
int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    QGraphicsScene scene;
    scene.setSceneRect(-300, -300, 600, 600);
    scene.setItemIndexMethod(QGraphicsScene::NoIndex);
 
    Spaceship *ship = new Spaceship;
    ship->setPos(0,0);
    scene.addItem(ship);
 
    QGraphicsView view(&scene);
    view.setRenderHint(QPainter::Antialiasing);
 
    view.setWindowTitle(QT_TRANSLATE_NOOP(QGraphicsView, "Spaceship"));
    view.resize(400, 300);
    view.show();
 
    QTimer timer;
    QObject::connect(&timer, SIGNAL(timeout()),&scene, SLOT(advance()));
    timer.start(1000 / 33);
 
    return app.exec();
}

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I was trying to modify the colliding mice example to just show a block move upward.

Thank you very much

Have you defined this two member functions: QRectF boundingRect() const;, QPainterPath shape() const;?

Also, make sure you've added both the header and the implementation files to your .pro file.

try cleaning the project, remove debug/release folders, remove the makefiles and the .pro.user file, then open the project again and rebuild.

You need to provide the implementations for two virtual functions (one pure) you declare:

Code:

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QRectF boundingRect() const;
QPainterPath shape() const;

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and the error goes away.

Thank you very much... I am an idiot