#include <QApplication>
#include <QDebug>

struct InnerClass;

struct OuterClass
{
    const QList<InnerClass*>& list() const
    {
        return _list;
    }
    QList<InnerClass*> _list;
};

struct InnerClass
{
    OuterClass const*const parent;

    InnerClass(OuterClass *parent)
        : parent { parent }
    {

    }

    int index() const
    {
        return parent->list().indexOf(const_cast<InnerClass*>(this));
    }
};

void test() {
    OuterClass outer;
    outer._list.append(new InnerClass(&outer));
    outer._list.append(new InnerClass(&outer));
    outer._list.append(new InnerClass(&outer));
    qDebug() << outer.list().last()->index();
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    test();

    return a.exec();
}