CRTP with Protected Derived Member

Question

In the CRTP pattern, we run into problems if we want to keep the implementation function in the derived class as protected. We must either declare the base class as a friend of

Answer 1

It's not a problem at all and is solved with one line in derived class:

friend class Base< Derived >;

#include 

template< typename PDerived >
class TBase
{
 public:
  void Foo( void )
  {
   static_cast< PDerived* > ( this )->Bar();
  }
};

class TDerived : public TBase< TDerived >
{
  friend class TBase< TDerived > ;
 protected:
  void Bar( void )
  {
   std::cout << "in Bar" << std::endl;
  }
};

int main( void )
{
 TDerived lD;

 lD.Foo();

 return ( 0 );
}