Strange casting error for qgraphicsview?

AndreAhmed

I have an object that inherits from QGraphicsitem, and it has an enum, when I write that code, it gives error for enum casting problem. Why that happens?

The problem is here :
@
Node *startItem =
qgraphicsitem_cast<Node *>(startItems.first());
Node *endItem =
qgraphicsitem_cast<Node *>(endItems.first());
@
@
if (mLink != 0 && mMode == Insert_Line) {
QList<QGraphicsItem *> startItems = items(mLink->line().p1());
if (startItems.count() && startItems.first() == mLink)
startItems.removeFirst();
QList<QGraphicsItem *> endItems = items(mLink->line().p2());
if (endItems.count() && endItems.first() == mLink)
endItems.removeFirst();

    removeItem(mLink);
    delete mLink;

    // if two nodes are connected by the line
    if (startItems.count() > 0 && endItems.count() > 0 &&
            startItems.first()&& endItems.first() &&
            startItems.first() != endItems.first()) {
        Node *startItem =
                qgraphicsitem_cast<Node *>(startItems.first());
        Node *endItem =
                qgraphicsitem_cast<Node *>(endItems.first());

        // add a line
        Link *arrow = new Link(startItem,endItem);
        arrow->trackNodes();
        addItem(arrow);
        arrow->updatePosition();

    }

@

koahnig

You should also post the error message.
Would be good to know the OS and compiler as well.

AndreAhmed

Thanks for reply.

Windows7, QTCreator, Mingw.

The error is

casting error <Node*>

and it is in that line:

Node *startItem =
qgraphicsitem_cast<Node *>(startItems.first());
Node *endItem =
qgraphicsitem_cast<Node *>(endItems.first());

my node class is :
@
class Node : public QGraphicsItem
{
Q_DECLARE_TR_FUNCTIONS(Node)
public:
enum Type { Input, Output};

public:

Node(QGraphicsItem *parent = 0, const Type& type = Input);
~Node();

void setText(const QString &text);

};
@

cincirin

quote from docs:

bq. To make this function work correctly with custom items, reimplement the "type()":http://qt-project.org/doc/qt-4.8/qgraphicsitem.html#type function for each custom QGraphicsItem subclass.

AndreAhmed

I just need a user defined enumeration, why should I reimplement type function?

cincirin

@template <class T> inline T qgraphicsitem_cast(QGraphicsItem *item)
{
return int(static_cast<T>(0)->Type) == int(QGraphicsItem::Type)
|| (item && int(static_cast<T>(0)->Type) == item->type()) ? static_cast<T>(item) : 0;
}
@

As you see item->type() is used in qgraphicsitem_cast function