Why VerticalHeaderItem cause crit.error

[Engelard]

When i add any action to my VertHItem - in runtime it cause crit error and the program stop working. I've included QHeaderView, certain Item indeed exist, but i simply can't set text for it:

if(tabWidGuide.verticalHeaderItem(0)->text()=="1") tabWidGuide.verticalHeaderItem(0)->setBackground(Qt::red);

That code assures that item at '0' exist and it's label is 1, which is true, it 1 by default in my app.

P.S. here is it in documentation

[mrjj]

Hi
You should check its not NULL
try
qDebug() << "item = " << tabWidGuide.verticalHeaderItem(0);

[jsulm]

@Engelard said in Why VerticalHeaderItem cause crit.error:

if(tabWidGuide.verticalHeaderItem(0)->text()=="1") tabWidGuide.verticalHeaderItem(0)->setBackground(Qt::red);

To add to @mrjj : you should ALWAYS check pointers before dereferencing them!

if(tabWidGuide.verticalHeaderItem(0) && tabWidGuide.verticalHeaderItem(0)->text()=="1") tabWidGuide.verticalHeaderItem(0)->setBackground(Qt::red);

[aha_1980]

@Engelard

And that's exactly the difference between pointers and references you have to understand.

Pointers have to be checked against nullptr before de-referencing, references can always be used.

[JonB]

@jsulm , @aha_1980
I agree with your advice. However, I took the OP at his word when his question states

[I am] certain Item indeed exist

I shall be interested to see whether he comes back and says that pointer was NULL after all, maybe I'm too trusting...!

[Engelard]

Tnx for all advices for checking item, now it shows that header does'nt exist. BUT. Why it exist in the app, and it returning like it does'nt?

[aha_1980]

@Engelard

Why it exist in the app, and it returning like it does'nt?

• How do you set it?
• Do you set it before your read it back?

[Engelard]

@aha_1980 i didn't set anything, i assume that it set by default, so why would i set it..

[aha_1980]

@Engelard said in Why VerticalHeaderItem cause crit.error:

i assume that it set by default,

It isn't.