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# sql/overview/subclass4/main.cpp Example File

    /****************************************************************************
    ** $Id: qt/main.cpp   3.3.0b1   edited Sep 10 12:50 $
    **
    ** Copyright (C) 1992-2002 Trolltech AS.  All rights reserved.
    **
    ** This file is part of an example program for Qt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #include "main.h"
    #include <qdatatable.h>

    InvoiceItemCursor::InvoiceItemCursor() :
        QSqlCursor( "invoiceitem" )
    {
        QSqlFieldInfo productName( "productname", QVariant::String );
        append( productName );
        setCalculated( productName.name(), TRUE );

        QSqlFieldInfo productPrice( "price", QVariant::Double );
        append( productPrice );
        setCalculated( productPrice.name(), TRUE );

        QSqlFieldInfo productCost( "cost", QVariant::Double );
        append( productCost );
        setCalculated( productCost.name(), TRUE );
    }

    QVariant InvoiceItemCursor::calculateField( const QString & name )
    {

        if ( name == "productname" ) {
            QSqlQuery query( "SELECT name FROM prices WHERE id=" +
                         field( "pricesid" )->value().toString() );
            if ( query.next() )
                return query.value( 0 );
        }
        else if ( name == "price" ) {
            QSqlQuery query( "SELECT price FROM prices WHERE id=" +
                         field( "pricesid" )->value().toString() );
            if ( query.next() )
                return query.value( 0 );
        }
        else if ( name == "cost" ) {
            QSqlQuery query( "SELECT price FROM prices WHERE id=" +
                         field( "pricesid" )->value().toString() );
            if ( query.next() )
                return QVariant( query.value( 0 ).toDouble() *
                                 value( "quantity").toDouble() );
        }

        return QVariant( QString::null );
    }

    int main( int argc, char *argv[] )
    {
        QApplication app( argc, argv );

        if ( createConnections() ) {
            InvoiceItemCursor invoiceItemCursor;

            QDataTable *invoiceItemTable = new QDataTable( &invoiceItemCursor );

            app.setMainWidget( invoiceItemTable );

            invoiceItemTable->addColumn( "productname", "Product" );
            invoiceItemTable->addColumn( "price",       "Price" );
            invoiceItemTable->addColumn( "quantity",    "Quantity" );
            invoiceItemTable->addColumn( "cost",        "Cost" );
            invoiceItemTable->addColumn( "paiddate",    "Paid" );

            invoiceItemTable->refresh();
            invoiceItemTable->show();

            return app.exec();
        }

        return 1;
    }