Item collision detection

Whether the player item collides with a coin is checked by the scene's checkColliding() function, which is called after the player item has moved horizontally or vertically.

Time for action - Making the coins explode

The implementation of checkColliding() looks like this:

void MyScene::checkColliding()
{
    for(QGraphicsItem* item: collidingItems(m_player)) {
        if (Coin *c = qgraphicsitem_cast<Coin*>(item)) {
            c->explode();
        }
    }
}

What just happened?

First, we call the scene's QGraphicsScene::collidingItems() function, which takes the item for which colliding items should be detected as a first argument. With the second, optional argument, you can define how the collision should be detected. The type of that argument is Qt::ItemSelectionMode, which was explained earlier. By default, an item will be considered colliding with m_player if the shapes of the two items intersect.

Next, we loop through the list of found items and check whether...