Cannot cast internal pointer of QModelIndex to custom class pointer

[antimatter]

Hello,
I have a QAbstractListModel subclass which has a QList with objects of type "struct Foo". For a custom paint job, I use QStyledItemDelegates for the view. Inside its paint() method, I'd like to handle the real object behind the item directly. So I tried getting it by casting the internal pointer of the model index. This will compile, but only yield 0.

Foo *f = static_cast<Foo*>(index.internalPointer());

Foo *f = static_cast<Foo*>(index.internalPointer());

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The problem here is, that the internal pointer is already 0. In the past I successfully used static casts on internal pointers.

On the other hand, using the model from the index and a custom method in the model works quite well. Yet, this solution looks rather long-winded.

Foo *f = ((FooModel*)index.model()).fooByIndex(index);
 
// Model definiton (excerpt)
class FooModel : public QAbstractListModel
{
public:
    Foo *fooByIndex(const QModelIndex &index);
}

Foo *f = ((FooModel*)index.model()).fooByIndex(index);

// Model definiton (excerpt)
class FooModel : public QAbstractListModel
{
public:
    Foo *fooByIndex(const QModelIndex &index);
}

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Am I missing something here or is the internal pointer supposed to be null?


Andreas