Re: [Boost-users] Determine Parent Class from boost::any

23 Nov 2009

      Hi!
what do you mean by parent? boost::any does not derive from any other class.
Just a note, using that version of cast:

       boost::any_cast(&any);
or
       boost::any_cast(&any);

will not throw, but return a null pointer if any does not contain the
expected type. Consider using boost::variant, which supports visitor-pattern
for dispatching.

Best Regards,
Ovanes

On Mon, Nov 23, 2009 at 5:18 PM, Yan Cheng Cheok  wrote:

...
May I know is there any way to determine parent class from boost::any?
#include <iostream>
#include 
class a {
public:
   virtual ~a() {}
};
class b : public a {
};
bool is_class_a(const boost::any& any)
{
   return boost::any_cast<a>(&any) != 0;
}
bool is_class_a_v2(const boost::any& any)
{
   try
   {
       boost::any_cast<a>(any);
       return true;
   }
   catch(const boost::bad_any_cast &)
   {
       return false;
   }
}
int main()
{
   std::cout<< is_class_a(b())<< std::endl;    // return 0. but i wish to
return 1.
   std::cout<< is_class_a(a())<< std::endl;    // return 1.
std::cout<< is_class_a_v2(b())<< std::endl; // return 0. but i wish to
return 1.
   std::cout<< is_class_a_v2(a())<< std::endl; // return 1.
}
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Re: [Boost-users] Determine Parent Class from boost::any

Ovanes Markarian