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List:       kde-devel
Subject:    Re: KDialogBase problem with KGuiItem
From:       David Faure <david () mandrakesoft ! com>
Date:       2001-11-29 17:09:11
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On Thursday 29 November 2001 17:46, Martijn Klingens wrote:
> Short question: is it possible to add a copy constructor and/or operator= to 
> QObject derived classes? I need to be able to copy those objects, or I will 
> have a much bigger problem. And the copy ctor in QObject is private, which 
> makes me seriously doubt whether this will work.

You can't do that, QObjects can't be copied.

> Long question (in case the short question resolves to 'no'):
> I am having a problem with KDialogBase. I want to change KGuiItem into a 
> QObject so I can emit signals from a gui item. But that has some 
> complications for KDialogBase.

I think QObject is a bit too heavyweight for KGuiItem. We already have KAction
for the "object that can be activated" concept. KGuiItem was supposed to be
only a repository of some settings, nothing more.

> If I drop the copy ctor and operator= the problem moves to KDialogBase, which 
> takes a 'KGuiItem&' and hence tries to make copies of the arguments. So I 
> changed the type into 'KGuiItem *' instead. But that in turn breaks the 
> implicit conversion from QString.

You can use a reference just like a pointer, using &arg. But in both cases
this relies on the caller not destroying the object, if you don't copy it.

> And now I wonder what to do. I can see only one solutions of which I'm pretty 
> sure it will work: add a whole slew of additional constructors to KdialogBase 
> that take Qstrings, next to those that take KGuiItems. But that is ugly code 
> at its best IMO.
> 
> Like I said, adding a copy ctor and operator= to KGuiItem would by far be the 
> best approach, but will it work? And otherwise, any ideas on how to solve 
> this?

I think the first step is to re-evaluate the idea of emitting signals from KGuiItem.
Then, if you really want to do that, you can use &arg to get the address of the
argument, with no need for copying it.

-- 
David FAURE, david@mandrakesoft.com, faure@kde.org
http://perso.mandrakesoft.com/~david/ , http://www.konqueror.org/
KDE 3.0: Konquering the Desktops
 
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