c++ - converting a base class pointer to a derived class pointer

Question

#include 
using namespace std;

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

template
class Derived: public Base {
  T _val;
public         


        

Answer 1

Try this:

Derived * d = static_cast* >(b);

downside it is, that you can cast class that is instance of Base() and then d->raw() will be undefined (segmentation fault likley). If that can be case, use dynamic_cast and have at least one function ob base virtual (having destructors virtual is essential when working with polmorphism).

Virtual functions are under the hood implemented using pointer on virtual table. This pointer can be also used to identify true type of class. This is used by dynamic_cast to check if this conversion can be done and brings small extra overhead when casted.