Update combobox data

rudag

I have no idea what happened but it just stopped working! Maybe because I've updated QT recently?

Now the application crashes when I call QSqlTableModel select() method. I'm getting the following:

The inferior stopped because it received a signal from the operating system.
Signal name: SIGSEGV
Signal meaning: Segmentation fault

jsulm

@rudag I guess it crashes here?

((QSqlTableModel*)ui->comboBox->model())->select();

As you can see you're dereferencing several pointers here. If one of them is invalid your app will crash with SIGSEGV. Does your combo box have a model? Does ui->comboBox point to a valid combo box instance? What does

qDebug() << ui->comboBox->model();

output?

JonB

@rudag
If you're using ((QSqlTableModel*)ui->comboBox->model()), don't! Always use object_cast (or whatever it is) from Qt, and check the return result for NULL. There are so many posts here which fall foul of this....

rudag

@jsulm
Yes and yes. It outputs: QSqlTableModel(0x20926780)

@JonB
I tried as you said:

QSqlTableModel *mod = qobject_cast<QSqlTableModel *>(ui->comboBox->model());
mod->select();

And it's still crashing. I can call other methods like mod->tableName() and it works normal. I guess the problem is with the select() method. Using it is the only way I found to reload the combobox model. Is there any other way?

jsulm

@rudag said in Update combobox data:

QSqlTableModel *mod = qobject_cast<QSqlTableModel *>(ui->comboBox->model());
mod->select();

You forgot to check the pointer.

rudag

@jsulm
The pointer is poiting correctly. Problem is with the method select().

I'm trying to do this in another way now without using relation models.

mapper->addMapping(ui->comboBox, model->fieldIndex("category"));
...
void MainWindow::loadCategories()
{
    ui->comboBox->clear();

    QSqlQuery q;
    int i = 1;
    q.exec("SELECT id, name FROM categories");
    while(q.next())
        ui->comboBox->insertItem(i++, q.value(1).toString(), q.value(0).toString());
}

My problem now is that it's not mapping the combobox data (insertItem() third argument). Am I missing something?

SGaist

Hi,

Can you show the stack trace of your crash ?

If the combo box is read-only, you might also want to consider a QSqlQueryModel.

rudag

@SGaist
Eureka! It's working with QSqlQueryModel. I'm using setQuery() instead of select() and it's refreshing perfectly.

By the way, QSqlQueryModel has no fieldIndex() method. Is there any similar method so I don't have to put the index static?

SGaist

You can get the QSqlRecord for your query and then use it to get what you want.