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  1. #include <type_traits>
  2. #include <utility>
  3.  
  4. template<typename T1, typename... Types>
  5. class Base
  6. {
  7. 	public:
  8. 	//assignment to base or derived class
  9. 	template<typename T, typename std::enable_if<std::is_base_of<Base<T1, Types...>, typename std::decay<T>::type>::value>::type* = nullptr>
  10. 	Base& operator=(T&& other)
  11. 	{
  12. 		if (this != &other)
  13. 			a = other.a;
  14. 		return *this;
  15. 	}
  16.  
  17. 	//assignment to other type contained in <T1, Types...>
  18. 	 template<typename T, typename std::enable_if<!std::is_base_of<Base<T1, Types...>, typename std::decay<T>::type>::value>::type* = nullptr>
  19. 	Base& operator=(T&& other)
  20. 	{
  21. 		// do some stuff
  22. 		return *this;
  23. 	}
  24.  
  25.  
  26. 	private:
  27. 	int a;
  28. };
  29.  
  30. class Derived : public Base<int, double>
  31. {
  32. 	public:
  33. 	// similar pattern here, but call base class' operators
  34. 	// for both copy/move assignment
  35. 	// as well as assignment to int or double
  36. 	template<typename T>
  37. 	Derived& operator=(T&& other)
  38. 	{
  39. 		Base<int, double>::operator=(std::forward<T>(other));
  40. 		return *this;
  41. 	}
  42. };
  43.  
  44. int main() {
  45. 	Derived foo;
  46. 	int a = 4;
  47. 	foo = a;
  48. 	return 0;
  49. }
Success #stdin #stdout 0s 3336KB
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https://ideone.com/turf2w
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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