How to get the indexvalue of a column with a relation set in QSqlRelationalTableModel?

Question

In QsqlRelationalTableModel foreign keys are resolved to human readable strings, if a relation for the column containing a foreign key is set. In my application stationids are resolved to stationnames.

For some purposes i need the stationid too. QsqlRelationalTableModel.data() or QsqlRelationalTableModel.itemData() only return the displayValue (for displayrole as well as for editrole). How can i get the corresponding foreign key (indexValue)?

Answer 1

QsqlRelationalTableModel.relationModel() returns a QSqlTableModel object for accessing the table for which column is a foreign key.

http://doc.qt.io/qt-5/qsqlrelationaltablemodel.html#relationModel

By the setFilter() method of relationModel() the corresponding id (indexValue) can be found, if the displayValue is unique:

rm = self.relationModel(<index column>)
f = '<columnname> = "{}"'.format(<displayvalue>)
rm.setFilter(f)
id = rm.data(rm.index(0,0))