CODEWITHSUNDEEP
c++qttypesdetection
Tomathor
Tomathor

Reputation: 41

How to detect what class an object is from? Qt

I'm programming a physicssimulation in QT with balls and this is the collision detection I'm using to detect collision between balls.

bool Ball:: circCollide(QList <QGraphicsItem *> items) {
    QPointF c1 = mapToScene( this->boundingRect().center());
//    qDebug() << "c1x" << c1.x();
//    qDebug() << "c1y" << c1.y();
//    qDebug() << "Listcount3: " << scene()->collidingItems(this).count();

    foreach (QGraphicsItem * t, items) {
//      qDebug() << "Classname: " << typeid(t).name();
//        if (typeid(t).name() == "Ball")
        if ( t->boundingRect().width()<200)
        {
            double distance = QLineF(c1,mapToScene( t->boundingRect().center())).length();
    //        qDebug() << "tx" << mapToScene(t->boundingRect().center()).x();
    //        qDebug() << "ty" << mapToScene (t->boundingRect().center()).y();
            double radius1 = this->boundingRect().width() / 2;
            double radius2 = t->boundingRect().width() / 2;
            double radii = radius1 + radius2;
    //        qDebug () << "distance radius1: " << radius1;
    //        qDebug () << "distance radius2: " << radius2;
    //        qDebug () << "distance :" << distance;
            if ( distance <= radii )
            {
            //    qDebug() << "true collision";
                return true;
            }
        }
    }
 //   qDebug() << "false collision";
    return false;
}

Now I have the problem that this sometimes is also called for when they collide with my walls. The balls have the Class Ball which I made myself and inherits from QGraphicsItem, while the walls have the class QLineF which also inherits from Qgraphicsitem. Is there any good way to figure out whether an object "t" belongs to the class Ball? I've already tried 

typeid(t).name()

but that returns the same for both classes (P13QGraphicsItem).

Also the list I feed to at the beginning contains all objects colliding with this item hence I have to feed it a list of QGraphicsItems.

Upvotes: 0

Views: 1809

Answers (3)

Rom&#225;rio
Rom&#225;rio

Reputation: 1966

If Ball is derived from QObject, and has the Q_OBJECT macro in its declaration, you can simply call QObject::metaObject and QMetaObject::className:

t->metaObject()->className();

Upvotes: 1

Alexander Tyapkov
Alexander Tyapkov

Reputation: 5067

You can try casting similar to this example:

Tag* tag = new Tag();
Polygon* polygon = new Polygon();
Polygon* polygon_cast = dynamic_cast<Polygon*>(polygon);
if(polygon_cast) qDebug() << "Cool!";
else qDebug() << "oh..";
Tag* tag_cast = dynamic_cast<Tag*>(tag);
if(tag_cast) qDebug() << "Cool!";
else qDebug() << "oh..";

Upvotes: -1

jwde
jwde

Reputation: 650

Override QGraphicsItem::type in Ball. Return something above the value of UserType and then call type on each QGraphicsItem to determine if it is a Ball.

Upvotes: 2

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