From: boost-users-bounces@lists.boost.org
[mailto:boost-users-bounces@lists.boost.org] On Behalf Of Ovanes Markarian
Sent: 03 August 2009 18:32
To: boost-users@lists.boost.org
Subject: Re: [Boost-users] variant: bounded types derive from same base
class
sorry, forgot to derive ABCDerived1 form ABCBase ;) But hope you got the
intention.
On Mon, Aug 3, 2009 at 5:33 PM, Ovanes Markarian
wrote:
Hi!
The only solution I can come up with is the declaration of the visitor in
your ABCBase as virtual function and visitor has a function template to
dispatch different types:
class ABCVisitor
{
public:
template<class T>
void visit(T& t)
{
// no visit implemented ...
}
};
class ABCBase
{
//... dtor, copy ctor, assignment operator etc.
public:
void accept_visitor(ABCVisitor& v)
{
do_accept_visitor(v);
}
private:
virtual void accept_visitor(ABCVisitor& v)=0;
};
class ABCDerived1 : public ABCBase
{
//... dtor, copy ctor, assignment operator etc.
void accept_visitor(ABCVisitor& v)
{
v.visit(*this);
}
};
template<>
void ABCVisitor::visit<ABCDerived1>(ABCDerived1& derived)
{
// handle derived here...
}
Hope that helps,
Ovanes
----------------------------------------------------------------------------
-----------------
Unfortunately, that would require changing the ABCBase to add those 2
member functions.
I can't touch ABCBase nor
Really, I have an existing hierarchy of classes which I cannot touch, but I
still would like to have
"external" polymorphism behaviour without the need to add base class virtual
functions.
Rds,
