[Interest] QSqlRelationalModel and QDataWidgetMapper: can items in QComboBox be filtered?

[Dmitry Teslenko]

Hello!

There's nice qt docs example here:
http://doc.qt.nokia.com/4.7-snapshot/sql-sqlwidgetmapper.html
demonstrating QSqlRelationalTable, QDataWidgetMapper and QComboBox.

They setup model:
	...
  	query.exec("create table person (id int primary key, "
                "name varchar(20), address varchar(200), typeid int)");
	...
	query.exec("create table addresstype (id int, description varchar(20))");
	...
	 model = new QSqlRelationalTableModel(this);
     model->setTable("person");
     model->setEditStrategy(QSqlTableModel::OnManualSubmit);

     typeIndex = model->fieldIndex("typeid");

     model->setRelation(typeIndex,
            QSqlRelation("addresstype", "id", "description"));
     model->select();

and then setup mapper:
     QSqlTableModel *relModel = model->relationModel(typeIndex);
     typeComboBox->setModel(relModel);
     typeComboBox->setModelColumn(relModel->fieldIndex("description"));

     mapper = new QDataWidgetMapper(this);
     mapper->setModel(model);
     mapper->setItemDelegate(new QSqlRelationalDelegate(this));
     mapper->addMapping(nameEdit, model->fieldIndex("name"));
     mapper->addMapping(addressEdit, model->fieldIndex("address"));
     mapper->addMapping(typeComboBox, typeIndex);


Here's the question: is there a way to filter typeComboBox items while
editing a record? Say, on button click. User clicks button and theres
types with some property only in typeComboBox.
I've tried two things:
1) calling setFilter on relModel. This somehow "decouples" combobox
from mapper and no further updates from typeComboBox pass to model.
2) setting typeComboBox::setModel() to relModel wrapped in
QSortFilterProxyModel. This causes invalid values to assigned. Say,
I picked second item in filtered list and mapper assigned second
item in not filtered list to model.

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