display a line number of my tableView not working

[aziz sahnoun]

Hi, i'm trying here to display on my label_9 the number of the selected line of my table so i used this code
Capture.jpg

and the problem is that label_9 is not taking any number
Capture.PNG

i used also

int k = ui->tableView->currentIndex().row();
ui->label_9->setNum(k)

int k = ui->tableView->currentIndex().row();
ui->label_9->setNum(k)

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and the lable is keep showing me -1 !