In my form I have a combobox cb_owner which must contain the pseudonym names of all the car owners, which are in the driver table. The combobox shows the name of the driver who owns the specific car. it should be possible to change the owner of the car by selecting a different name in the combobox.

The program so far works allmost: If the driver_id field in a record in the cars table contains a correct id, the combobox does show the correct owmer, and the combobox does contain the all the pseudonym names from the driver table, but what do i need to do in order to update the driver_id field in the cars table to the driver selected in the combobox.

Do I need Item delegation? And how should I use it?

I've seen the books example, but I don't want to use the QTableView.
I've also seen the SQLWidgetmapper example, but that one does not work correctly. It does not update the addresstype_id in my database.

I've also thought of using a slot on the combobox. I think the slot on_cb_owner_activated(int index), but I don't know what I should update, when the user selects another driver from the combobox.

void Form_cars::on_cb_owner_activated(int index)
{
//What should I do over here?
}

This is the code from the constructor:

Form_cars::Form_cars(QWidget *parent) :
QWidget(parent),
ui(new Ui::Form_cars)
{
ui->setupUi(this);

model = new QSqlRelationalTableModel(this);
model->setTable("T_SRM_cars");
model->setEditStrategy(QSqlTableModel::OnManualSubmit);

// Remember the indexes of the columns
driver_id = model->fieldIndex("driver_id");

// Set the relations to the other database tables
model->setRelation(driver_id, QSqlRelation("T_SRM_drivers", "id", "pseudonym"));

model->select();

ui->cb_owner->setModel(model->relationModel(driver_id));
ui->cb_owner->setModelColumn(model->relationModel(driver_id)->fieldIndex("pseudonym"));

mapper = new QDataWidgetMapper(this);
mapper->setModel(model);

mapper->addMapping(ui->le_name, model->fieldIndex("name"));
mapper->addMapping(ui->cb_owner, driver_id);
mapper->addMapping(ui->le_brand, model->fieldIndex("brand"));
mapper->addMapping(ui->le_model, model->fieldIndex("model"));

if (model->rowCount()==0) {
    model->database().transaction();
    if (model->insertRow(model->rowCount())) {
        mapper->toLast();
    } else {
        QMessageBox::warning(this, tr("T_SRM_drivers"),
                             tr("The database reported an error: %1")
                             .arg(model->lastError().text()));
    }
}

mapper->toFirst();

}

Regards,

Gerrit Zijlstra