Strange selectionModel()->selectedRows() problem.

Chrisw01

Hi,

Can someone give me a heads up on why the following code would stop working after adding data to a SQL database?

 QModelIndexList selectedRows = ui->equipmentTableWidget->selectionModel()->selectedRows();

This function is inside a slot that is called when the selections are changed. It returns the proper values until I add information to the table and update a SQL database. After that selectedRows.count() is always 0 until I exit the program and start over again. At this point it works fine but if I add another item to the table and database it starts returning 0 again.

Using windows 7 with QT 5.9.1 and minGW compiler.

Thanks

SGaist

Hi,

Can you show the code you wrote that interacts with the model and database ?

Chrisw01

Hi,

Here is the code that calls the dialog and adds to the database.

void MainWindow::processNewEquipment()
{
    equipmentDialog dialog;

    if(dialog.exec() == dialog.Accepted) {
        QSqlQuery sql;
        sql.prepare(EQUIPMENT_TABLE_INSERT);
        sql.bindValue(":equipmentID", dialog.getEquipmentID());
        sql.bindValue(":equipmentDescription", dialog.getEquipmentDescription());
        sql.bindValue(":equipmentIDNumber", dialog.getEquipmentIDNumber());
        sql.bindValue(":equipmentPurchaseMileage", dialog.getEquipmentPurchaseMileage());
        sql.bindValue(":equipmentCurrentMileage", dialog.getEquipmentCurrentMileage());
        sql.bindValue(":equipmentCurrentOperator", dialog.getEquipmentCurrentOperator());
        sql.bindValue(":equipmentPurchasePrice", dialog.getEquipmentPurchasePrice());
        sql.bindValue(":equipmentExpenses", dialog.getEquipmentExpenses());
        sql.bindValue(":equipmentIncomeGenerated", dialog.getEquipmentIncomeGenerated());
        sql.bindValue(":equipmentLicenseNumber", dialog.getEquipmentLicenseNumber());
        sql.bindValue(":equipmentNotes", dialog.getEquipmentNotes());
        if(sql.exec()) {
            QMessageBox::information(this, "processNewEquipment", tr("New Equipment added to the database!"));
            loadEquipmentDatabase();
        }
        else QMessageBox::critical(this, tr("Error:: "), sql.lastError().text());
    }
}

And this is the code that loads the table.

void MainWindow::loadEquipmentDatabase()
{
    QSqlQueryModel * model = new QSqlQueryModel();
    QSqlQuery * sql = new QSqlQuery();

    sql->prepare(EQUIPMENT_TABLE_READ_ALL);
    if(sql->exec()) {
        model->setQuery(*sql);
        ui->equipmentTableWidget->setModel(model);
    }
    else QMessageBox::critical(this, tr("Error::"), sql->lastError().text());
}

Thnks

Chrisw01

After further testing, it has something to do with the second call to loadEquipmentDatbase(); if I comment out that line it still works fine just the table is not updated.

SGaist

Each time you call loadEquipmentDatabase you create a new model, why ? Just replace the query. By the way why are you allocating the QSqlQuery object on the heap ?
By the way, why not call model->setQuery(EQUIPMENT_TABLE_READ_ALL) ?

Chrisw01

When I did research on filling a QTableWidget from SQL that is what I come up with. Can you provide an example on how to do this correctly?

VRonin

just

move QSqlQueryModel * model = new QSqlQueryModel(); and ui->equipmentTableWidget->setModel(model); in the constructor
change model->setQuery(*sql); to ui->equipmentTableWidget->model()->setQuery(sql);
change QSqlQuery * sql = new QSqlQuery(); to QSqlQuery sql;

Chrisw01

Hi and thanks for the info, however ui->equipmentTableWidget->model()->setQuery(sql); generates the following error.

error: 'class QAbstractItemModel' has no member named 'setQuery'
     ui->equipmentTableWidget->model()->setQuery(EQUIPMENT_TABLE_READ_ALL);
                                        ^

So what I did was per your advice moved the suggested code to the constructor. then in my loadEquipmentDatabase() function I placed

QSqlQueryModel *model = qobject_cast<QSqlQueryModel*>(ui->equipmentTableWidget->model());
    if(model)
        model->setQuery(EQUIPMENT_TABLE_READ_ALL);

Not sure if that is the proper way but it works as expected now.

Thanks.