[Interest] type casting 5 levels down no error but not proper

[Sujan Dasmahapatra]

[code]
QWidget *wid  = qobject_cast<QWidget *>(parent());
CSheet *sheet = qobject _cast<CSheet *>(wid->parent());
QScrollArea *scrollArea = qobject _cast<QScrollArea *>(sheet->parent());
CTabWidget *tabWid = qobject _cast<CTabWidget *>(scrollArea->parent());//Here it is crashing, QSSERT(d)  failure
CDataPage  *dataPage = qobject _cast<CDataPage *>(tabWid->parent());
MainWindow *mainwin = qobject _cast<MainWindow *>(dataPage->parent());
mainwin->statusBar()->showMessage(tr("A new plot being added!!"),5000);
[/code]

Dear Konstantin

It's not returning anything, it's crashing. When casting to get CTabWidget. For the sheet's parent is QScrollBar so I am getting that by scrollArea and scrollArea's parent is CTabWidget.....which is getting failure. What could be the possible reason, please help. 

Kind regards,


Sujan Dasmahapatra
Project Leader, Aero Group
CE - Aero Group

Tel  +91 80 66470248
Mob  
sdh at lmwindpower.com


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-----Original Message-----
From: Konstantin Tokarev [mailto:annulen at yandex.ru] 
Sent: Tuesday, April 24, 2012 6:17 PM
To: Sujan Dasmahapatra
Cc: interest at qt-project.org
Subject: Re: [Interest] type casting 5 levels down no error but not proper


24.04.2012, 16:42, "Sujan Dasmahapatra" <sdh at lmwindpower.com>:
> Thanks Diego and Konstantin for your valuable inputs. I am now doing qobject_cast for all of them, please check the code snippet below, now it’s crashing at tabWid step. It’s giving QASSERT failure. The failure is happening in the following file
>
> //qscopedpointer.h at the following line QASSERT(d)
>
>   inline T *operator->() const
>
>     {
>
>         Q_ASSERT(d); //this line it’s crashing.
>
>         return d;
>
>     }

It means that tabWid is QScopedPointer with 0 value. You need to check if qobject_cast doesn't return 0 before using pointer.

-- 
Regards,
Konstantin