[Qt-interest] moc / multiple inheritance issue

[Girish Ramakrishnan]

Haven't tried the code but I don't think this has anything to do with
moc. c-style casting + multiple inheritance is the issue. You should do
something like
(dynamic_cast<DeclareYourself *> specialLineEdit)->declareYourself();

Girish

Jimmy Cooksey wrote:
> Hello Everyone,
> 
> I'm experiencing a strange problem where moc appears to be hijacking a
> method call to my object that is multiply inheriting from some widget
> and another base class.
> 
> Here is some sample code:
> 
> // This is the base class
> class DeclareYourself
> {
> 	public:	
> 	DeclareYourself() { };
> 	virtual ~DeclareYourself() { };
> 	virtual void declareYourself() = 0;
> };
> 
> class SpecialLineEdit : public QLineEdit, public DeclareYourself
> {
> 
> 	Q_OBJECT
> 
> 	public:
> 	SpecialLineEdit(QWidget* parent) : QLineEdit(parent), DeclareYourself();
> 	~SpecialLineEdit() { }
> 	void declareYourself()
> 	{
> 		setText("I'm a line edit!");
> 		return;
> 	}
> };
> 
> So when I create this object, I'm using something like...
> QWidget* specialLineEdit = new SpecialLineEdit(this);
> 
> The interesting thing is that this call...
> ((*DeclareYourself) specialLineEdit)->declareYourself();
> ... never calls SpecialLineEdit::declareYourself()
> It immediately calls this:
> SpecialLineEdit::qt_metacall(QMetaObject::Call _c, int _id, void **_a)
> and of course, I have no idea why.
> 
> The code itself compiles just fine, and the application does not crash.
> 
> I have created a sample project demonstrating my problem:
> http://www.jimster.org/QtTestCase.zip
> 
> Any help would be greatly appreciated!
> 
> Thanks,
> Jimmy