[PATCH] KFileDialog overwrite confirmation

Michael Pyne mpyne at purinchu.net
Mon Jul 14 02:55:40 BST 2008

On Sunday 13 July 2008, Rafael Fernández López wrote:
> Hi,
> > You could then have a non-virtual function in KAbstractFileWidget whose
> > implementation packages up the parameters for virtual_hook() and then
> > calls virtual_hook().  Subclasses would then have to reimplement
> > virtual_hook() if they needed to change the behavior though so it may not
> > be the best way I guess if there's an easier way.
> Cool !! Didn't notice it ! The question now is, does it need to be virtual
> ?

A class's implementation does not need to be but you would need to redefine 
virtual_hook() in the subclass if a different implementation is desired:

i.e.: (2 space shiftwidth for email purposes)

void KAbstractFileWidget::setConfirmOverride(bool b)
  virtual_hook(0, static_cast<void*>(&b)); // 0 is id of call

Now in a subclass:

void KFileWidget::virtual_hook(int id, void *data)
  if(id == 0) // setConfirmOverride(bool)
    bool *b = static_cast<bool*>(data);
    setConfirmOverrideInternal(b); // not virtual
    // Unhandled, pass it to superclass.
    KAbstractFileWidget::virtual_hook(id, data);

Since the implementation is done in virtual_hook, and 
KAbstractFileWidget::setConfirmOverride() calls virtual_hook(), the right 
virtual implementation will always get called.  KFileWidget's implementation 
could be changed by handling virtual_hook() in a subclass.

Now if for whatever reason you override setConfirmOverride() in a subclass you 
would need to ensure calling virtual_hook() as setConfirmOverride() cannot be 
virtual, but there's really no reason to override setConfirmOverride in a 
subclass, the reimplementation belongs in virtual_hook().

 - Michael Pyne
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