core/crtp.cpp

The following code example is taken from the book
C++23 - The Complete Guide by Nicolai M. Josuttis, Leanpub, 2026
The code is licensed under a Creative Commons Attribution 4.0 International License.

---

// raw code

#include <iostream>

template<typename DerivedT>
class Base
{
public:
  void callFoo() {
    static_cast<DerivedT*>(this)->foo(); // calls the foo() member for the derived object type
  }
};

class D1 : public Base<D1>
{
public:
  void foo() {     // foo() of derived type D1
    std::cout << "D1::foo()\n";
  }
};

class D2 : public Base<D2>
{
public:
  void foo() {     // foo() of derived type D2
    std::cout << "D2::foo()\n";
  }
};

int main()
{
    D1 d1;
    d1.callFoo();  // calls D1::foo() via Base::callFoo()

    D2 d2;
    d2.callFoo();  // calls D2::foo() via Base::callFoo()
}