Example for enable_if_t

enable_if_t.cpp

// Ref: https://en.cppreference.com/w/cpp/types/enable_if
#include <type_traits>
#include <iostream>


struct TypeTrue {
    static constexpr bool enable_if_condition = true;
};

struct TypeFalse {
    static constexpr bool enable_if_condition = false;
};

template <typename T>
class MyClass {
  public:
    template <typename C = T>
    typename std::enable_if_t<!C::enable_if_condition, void>
    test_fxn() {
      if (T::enable_if_condition) {
        std::cout << "AAAA" << std::endl;
      }
      std::cout << "BBBB" << std::endl;
    }

    template <typename C = T>
    typename std::enable_if_t<C::enable_if_condition, void>
    test_fxn() {
      if (T::enable_if_condition) {
        std::cout << "CCCC" << std::endl;
      }
      std::cout << "DDDD" << std::endl;
    }
};

int main() {
  MyClass<TypeTrue> a;
  MyClass<TypeFalse> b;
  a.test_fxn();
  b.test_fxn();
  return 0;
}