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

You can use dynamic_cast

Derived * d = dynamic_cast *>(b);

If the cast fails (the base pointer does not point to the requested derived type), it returns null.

However, for dynamic_cast to work, your base class must have at least one virtual function. I suggest you make the destructor virtual (this is also prevents other potential problems deleting your objects).

Use of dynamic_cast may indicate bad design in your code.

Note that if you are 100% sure the base pointer, points to your derived type, then you may replace it with static_cast, which is slightly faster. Personally I prefer the extra safety check in general.