QTableManager Removing All Rows Crashes Application with Bad Access

maximo

I have a QTableWidget that I drew in QT Creator, as well as added rows there. I tried using the following techniques...

http://stackoverflow.com/questions/15848086/how-to-delete-all-rows-from-qtablewidget

...but the application crashes with a bad access after it removes all the rows.

However, if I leave one row behind, it doesn't crash. For instance:

ui->myTable->model()->removeRows(0,ui->myTable->rowCount()-1);
// leaves a row, but doesn't crash; remove -1 and it removes all rows and crashes

...and...

for (int i = 0; i<= ui->myTable->rowCount(); i++) {
    ui->myTable->removeRow(0);
}
// leaves a row, but doesn't crash; set i = -1 and it removes all rows and crashes

Did I stumble upon a huge showstopper bug in Qt 5.5?

EDIT: Hang on...may be because later on in the code I'm trying to select a row that no longer exists....

Olivier Ronat

@maximo
Hello.
I rapidly draw an application designing a QTableView with QDesigner adding 2 rows and a PushButton with the following code
void MainWindow::on_pushButton_clicked()
{
ui->tableWidget->model()->removeRows(0,ui->tableWidget->rowCount());
}

I have no crash.

In fact you use to remove the model rows with the rowCount of the Table. Perhaps you may try to use ui->myTable->model()->removeRows(0,ui->myTable->model()->rowCount()); to be coherent.

But is the model of your QTableWidget or your QTableWidget itself connected to another QObjet?

maximo

@Olivier-Ronat Thanks for checking, Olivier. Sorry to detain you to do that when I found it was my own fault. However, I learned some things and got a little better at debugging in Qt Creator.

I found the cause. I had a signal attached to the selectionModel of each row. Here's how I found out (note, I'm a newbie). On my Mac, I got the crash report and clicked a button to see what it was. This showed a callstack. I was able to see that it was complaining about setting text() from on_SelRow, and then I recalled that I had a signal connected on rows. So, I changed my code like so:

ui->myTable->selectionModel()->disconnect();
ui->myTable->model()->removeRows(0,ui->myTable->rowCount());

I was then able to remove rows without a crash. I just need to remember to add the signal back to the table when I add rows again.

P.S.

You may also be wondering why I was intercepting a selected row. The reason was because then I could show a box above the table that showed the item detail in an easier to read format than having to scroll horizontally in the table to see all the columns. I was doing it like so:

connect(ui->myTable->selectionModel(), SIGNAL(currentRowChanged(QModelIndex,QModelIndex)),
                this, SLOT(on_SelRow(QModelIndex,QModelIndex)));

...and then I had a class method like so:

void MainWindow::on_SelRow(QModelIndex oCurrRow, QModelIndex oPrevRow)
{
    QTableWidget *t = dynamic_cast<QTableWidget *>(QObject::sender()->parent());
    int y = oCurrRow.row();
   // do something with t (table) and y (row index) variables
}