I am subclassing QSqlTableModel for a model used by a QListView.
This model represents data stored in a SQLite database.
In this database I have a flag field (let say an int field at column 0).
I want my model to present data depending on the flag value, in other word I want to apply a filter on my model.
So I have a public method setFilter(int flag) to set the current filter on flag value, and I want my model to present only the data (rows) that match this value.

Let say my db is like:
flag | value
0 | foo
1 | bar
After setFilter(0) I want my model to present only:
flag | value
0 | foo
The code :
MyModel::MyModel(QObject *parent) :

MyModel::setFilter(int flag) 
currentFlag = flag; // currentFlag is MyModel class member

MyModel::data(const QModelIndex & index, int role ) const
    if( index.model()->data(index.sibling(index.row(),0)) == currentFlag) // if the current index points to a row with flag column equals to the current filter, return the value, but this leads to infinite recursive call 
        return QSqlTableModel::data(index, role);
    else return QVariant(); // else return an invalid data
Problem is, to check the flag value I have to call data() inside the data() method, which leads to infinite recursive call.
How can I solve this ? How can I check value of another ModelIndex in the QAbstractItemModel::data() method ? Is it possible or am I using Model/view classes the wrong way ?

Hope everything is clear.