Re: downcasting template class with paramaterised parent

From:
"Alex Blekhman" <xfkt@oohay.moc>
Newsgroups:
microsoft.public.vc.language
Date:
Tue, 25 Jul 2006 19:27:48 +0300
Message-ID:
<e74KGdAsGHA.5044@TK2MSFTNGP05.phx.gbl>
<jason.saunders@gmail.com> wrote in message
news:1153842625.988982.183970@h48g2000cwc.googlegroups.com...

I have a situation where I have a number of MFC derived
classes. For
example two classes are;

class MyEdit : public CEdit

and

class MyButton : public CButton

I want to derive MyEdit and MyButton from a common class
but to retain
the MFC inheritance.

Therefore I introduced a template class which has the
parent as a
parameter, e.g.;

template <class PARENT>
class MyControl : public PARENT

I now want to implement some common functionality in the
MyControl
class, e.g.;

template <class PARENT>
class MyControl : public PARENT
{
  ...
  Common()
  {
     // Do something
  }
  ...
}

I want to be able to call the Common method without
knowing the runtime
type of the object. I have a pointer to a CWnd which can
be downcast
to a MyButton or MyEdit.

How do I cast the CWnd pointer appropriately to call the
Common method?


You cannot, since MyControl is not a type. So there is no
type to downcast to. MyControl<T> will become a type when
it's instantiated.

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