internalPointer always null on a QSqlRelationalTableModel subclass using a treeview

Version : QT 4.7.3 (mingw) / win XP

Data :

SQL table group ( id, name )
SQL table students ( id, name, group_id )

Issue :

Sub - classing QSqlRelationalTableModel in order to have on a treeview :

• toplevelitems : content of group
• children of toplevelitems : content of students for a given group ( with group_id)

I use QSqlRelationalTableModel because 'name' columns are in other tables.

All is going well except for the data function redefinition.
I have the good number of toplevelitems and for each item the good number of children.
But the data within the children is only the toplevel data repeated ( data function not working )

I have found out that the modelItem.internalPointer is always NULL in data function, even if I do set it within the index redefinition via createindex(row, column, (void*)data) (I set it to the SQLModel* for each child of toplevelitems).

I can't redefine the parent for modelIndex either since the QAbstractTableModel::parent() function is private, which could have helped me to know where I was within the 'tree' model inside the data redefinition.

Is there another way to achieve what I want to do ? Is it normal that internalPointer is always NULL ?

(model class code attached )

Thank you for the help,

Sebius.