Re: Does object have function?

What I am trying to accomplish: I have a map of polymorphic objects and
these objects may have certain methods defined or not. If the instance has
the method then I want to call it, otherwise not.

It is trivial to create a virtual function for a few functions. But I would
have to add every single function that could be interfaced.

I would just to somehow be able to tell if an instance has a function
available. Consider:

#include <iostream>

class Base {
public:
   virtual ~Base() {}
};

class DerivedOne : public Base {
public:
   void foo() { }
};

class DerivedTwo : public Base {
public:
   void foo() { }
};

class DerivedThree: public Base {
};

int main() {
   Base* bps[3];
   bps[0] = new DerivedOne();
   bps[1] = new DerivedTwo();
   bps[2] = new DerivedThree();

   for ( auto i = 0; i < 3; ++i ) {
      DerivedOne* thisOne = dynamic_cast<DerivedOne*>( bps[i] );
      if ( thisOne )
         thisOne->foo();
   }
}

I would have to dynamic_cast for every class that had a foo() defined to
execute all foos. Is there a way to do what I want?