QDataWidgetMapper and QSqlRelationalTableModel problem

Hi,

I have a problem using a QDataWidgetMapper together with a QSqlRelationalTableModel.

The db-table products has the following fields: product, vendor_id, description, baseprice, basecurrency_id, price. vendor_id and basecurrency_id are id's to different tables in the db. I created a QDataWidgetMapper adding various lineEdits and ComboBoxes into it. The comboxes are for the vendor_id and basecurrency_id which show the real value instead of just the index (standard releational db stuff). Having a table view showing all products allows me now to edit the data nicely. The problem starts when I add a new record into the database. I preset basecurrency_id using

Code:

productModel->setData(productModel->index(row, basecurrency_id), "USD");

. When I now edit the other fields, but don't touch the basecurrency_id combobox and try to submit the record I get an sql error saying something like incorrect integer value "USD". So, it seems that 'USD' gets written into the db instead of the index (=1). When I manually set it to 'USD' using the combobox everything works fine.

My question is - how do I set a value in the model which is tied to a relation? Or is there something else I'm doing wrong.
Thanks.

DB:

Code:

CREATE TABLE currencies (
id            SMALLINT UNSIGNED AUTO_INCREMENT,
currency      char(3) NOT NULL,
symbol        varchar(1) NOT NULL,
PRIMARY KEY (id)
);
 
INSERT INTO currencies VALUES (0, "USD", "$");
INSERT INTO currencies VALUES (0, "EUR", "E");
INSERT INTO currencies VALUES (0, "CAD", "$");
 
#
# products:
#
CREATE TABLE products (
id                 INT UNSIGNED AUTO_INCREMENT,
product            varchar(64) NOT NULL,
vendor_id          SMALLINT UNSIGNED NOT NULL,
description        text,
baseprice          DECIMAL(15,2) DEFAULT 0.00,
basecurrency_id    SMALLINT UNSIGNED NOT NULL,
price              DECIMAL(15,2) DEFAULT 0.00,
PRIMARY KEY (id)
);

Code to set QSqlRelationalTableModel and mapper

Code:

// Initialize model
	productModel = new QSqlRelationalTableModel(productTableView);
	productModel->setTable("products");
	productModel->setSort(2, Qt::AscendingOrder);
	productModel->setEditStrategy(QSqlTableModel::OnFieldChange);
 
 
    // Remeber the indexes of the columns
    vendor_id = productModel->fieldIndex("vendor_id");
    basecurrency_id = productModel->fieldIndex("basecurrency_id");
 
    // Set the relations to the other database tables
    productModel->setRelation(vendor_id, QSqlRelation("vendors", "id", "company"));
    productModel->setRelation(basecurrency_id, QSqlRelation("currencies", "id", "currency"));
 
	// set table header 
	productModel->setHeaderData(productModel->fieldIndex("product"), Qt::Horizontal, tr("Name"));
	productModel->setHeaderData(vendor_id, Qt::Horizontal, tr("Vendor"));
	productModel->setHeaderData(productModel->fieldIndex("baseprice"), Qt::Horizontal, tr("Base Price"));
	productModel->setHeaderData(basecurrency_id, Qt::Horizontal, tr("Base Currency"));
	productModel->setHeaderData(productModel->fieldIndex("price"), Qt::Horizontal, tr("Price"));
 
   // Populate the model
    if(!productModel->select()) {
        showError(productModel->lastError());
        return;
    }
 
	// Initialize table view
	productTableView->setModel(productModel);
	productTableView->resizeColumnsToContents();
   	productTableView->setSelectionMode(QAbstractItemView::SingleSelection);
 
	// hide fields in table
	// productTableView->setColumnHidden(productModel->fieldIndex("id"), true);
	productTableView->setColumnHidden(productModel->fieldIndex("description"), true);
 
	// set delegate
	// productTableView->setItemDelegate(new QSqlRelationalDelegate(productTableView)); 	
 
	// Initialize the combo boxes
    productBaseCurrencyComboBox->setModel(productModel->relationModel(basecurrency_id));
    productBaseCurrencyComboBox->setModelColumn(productModel->relationModel(basecurrency_id)->fieldIndex("currency"));
//	productBaseCurrencyComboBox->setCurrentIndex(0);
 
    productVendorComboBox->setModel(productModel->relationModel(vendor_id));
    productVendorComboBox->setModelColumn(productModel->relationModel(vendor_id)->fieldIndex("company"));
//	productVendorComboBox->setCurrentIndex(0);
 
	// Initialize widget mapper
   	mapper = new QDataWidgetMapper(this);
    mapper->setModel(productModel);
    mapper->setItemDelegate(new QSqlRelationalDelegate(productTableView));
    mapper->addMapping(productNameLineEdit, productModel->fieldIndex("product"));
    mapper->addMapping(productVendorComboBox, vendor_id);
    mapper->addMapping(productDescriptionTextEdit, productModel->fieldIndex("description"));
    mapper->addMapping(productBasepriceLineEdit, productModel->fieldIndex("baseprice"));
 	mapper->addMapping(productBaseCurrencyComboBox, basecurrency_id);
    mapper->addMapping(productPriceLineEdit, productModel->fieldIndex("price"));
 
    connect(productTableView->selectionModel(), SIGNAL(currentRowChanged(QModelIndex,QModelIndex)),
            mapper, SLOT(setCurrentModelIndex(QModelIndex)));
 
	mapper->setSubmitPolicy(QDataWidgetMapper::AutoSubmit);
	mapper->toPrevious(); 
	productTableView->setCurrentIndex(productModel->index(0, 0));

Code to insert a new row into the model

Code:

productModel->insertRows(row, 1);
		productModel->setData(productModel->index(row, productModel->fieldIndex("product")), "");		
		productModel->setData(productModel->index(row, productModel->fieldIndex("description")), "");		
		productModel->setData(productModel->index(row, productModel->fieldIndex("baseprice")), "0.00");		
		productModel->setData(productModel->index(row, basecurrency_id), "USD");		
		productModel->setData(productModel->index(row, productModel->fieldIndex("price")), "0.00");
 
		productTableView->setCurrentIndex(productModel->index(row, 0));