Question

I have some base class A, and some number of inherited classes:

class B : public A
class C : public A
class D : public A

I have function with parsing some config file, which use name in config call:

void do_smth<B>(...);
void do_smth<C>(...);
void do_smth<D>(...);

I have map<A*> objs; and in those functions happend:

void do_smth<T>(...)
{
  T *control = new T();
  ...
  objs[name] = T;
}

So i have map of pointers to A. In other function I got name, and i need to get value stored in B,C or D classes.
Problem is that i can’t add virtual function to any class which will return those value, because of A,B,C,D from library and B have function value(), C – text(), D – currentValue() etc. And i need function get_value() which will return result of value(), text(), currentValue() depending on class?
What can you advise me to solve my problem?

I see 2 ways:

1) I can write function from pointer to classes B,C,D and call function like that get_value((B*)objs[name]); but i think it’s not good.

2)I can create boost::bind object with function i need at the create B,C,D variable.

What way will be better, or could you advise me smth better?

Answer 1

So you have

A* a;

and don’t know what type it is. Try dynamic_cast:

B* b = dynamic_cast<B*>(a);
if ( b ) 
    return b->value();
//C and D the same way