Modify QtableWidget from a slots

mrjj

Hi
Yes it possible. and it normally just works

ui->tableWidget_2->item(0,0)->setText("Test");

changes the first row/col of the table widget

Yoyotl

Yeah, I was thinking that too, but it doesn't work...
Debugger sort that :

Christian Ehrlicher

@mrjj said in Modify QtableWidget from a slots:

ui->tableWidget_2->item(0,0)

I would guess this returns a nullptr since there is no QTableWidgetItem set yet - you have to set one before accessing it.

mrjj

Hi
You must assign items to the row/cols or else NULL is returned.
Try with

auto item = ui->tableWidget_2->item(row, 0);
if (item)
    item->setText("Test");
else
    qDebug() << "item is null";

Yoyotl

Itwork's if I put that in mainwindow, but if I put it in my slot like I want to do, the program crash again...

JonB

@Yoyotl
In your slot, put in debugging code to see how many rows/columns/what items your table has, before you try to dereference with table->item(rowToChange, 0). You are using the same table instance as you create with

QTableWidget* table = new QTableWidget(this);

aren't you, because that looks like a local variable.... ? If you have a QMainWindow member variable named table, then statement QTableWidget* table = new QTableWidget(this); is not setting the member one...

mrjj

@JonB
Ahhh good spotted. The dangling pointer classic :)

Yoyotl

Thanks for your answers.
First, I create table in my mainwindow.cpp, and I declare it in mainwindow.h in public.
My slot is in the file mainwindow.cpp
And I can't even test how many rows/columns/item I have in it in my slot, because program crash on a segmentation fault every time that I try to access to table on my slot
Do I need to declare table in antoher place/file ?

mrjj

@Yoyotl

QTableWidget* table = new QTableWidget(this); // this would be wrong as its a local variable

table = new QTableWidget(this); // this would allocate the one you have in the class. (in the .h )

so make sure to remove the first one so there is ONLY the one in the class that you access in the slot

Im 99% sure that is why you crash.

Yoyotl

IT WAS THAT !!
THANK YOU SO MUCH @mrjj !

So yes it was a problem in my declaration of table
That fix all my problems, thank you all !

mrjj

@Yoyotl
Actually it was @JonB that spotted it but
super its fixed :)