Cannot create a QAbstractItemModel::createIndex(r,c),

[tonnot]

I have a function to retrieve data from my model.
I want to call it using row,col (r,c) set by me.

return a_model->data(QAbstractItemModel::createIndex(r,c),Qt::DisplayRole);

return a_model->data(QAbstractItemModel::createIndex(r,c),Qt::DisplayRole);

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Ok, I get
error: cannot call member function 'QModelIndex QAbstractItemModel::createIndex(int, int, void*) const' without object

Any idea ?