[Qt-interest] Upcasting to Derived Widget crashes

[Srdjan Todorovic]

Hi,

2009/4/20 Neel Basu <neel.basu.z at gmail.com>:
> I've designed a QDockWidget Ui and made a QDockWidget Derived Class that wraps
> that ui.
> and while designing the main window in designer I make its a QDockWidget and
> latter in the Constructor I again assign a new DerivedQDockWidget to it.
>
> MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new
> Ui::MainWindowClass){
>  //delete ui->folderDock;
>  ui->folderDock = new FolderPane(this);

If you look at the uic generated header file, you should notice that
these pointers are not valid until you call setupUi().

ui->folderDock  should currently be an invalid pointer.

>  //delete ui->mailWidget;
>  ui->mailWidget = new MailListWidget(this);
>  ui->setupUi(this);

ui->folderDock  should now be a valid pointer.

> }
>
> But the above crashes.
> then I added corresponding delete s but it is still crashing

If it keeps crashing, then use a debugger.

> actual type of ui->folderDock is QDockWidget* and FolderPane inherits
> QDockWidget

Hope that helps,

Srdjan