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  1. #include <tuple>
  2. #include <iostream>
  3.  
  4. class Base
  5. {
  6.   public:
  7.     virtual ~Base(void){}
  8. };
  9.  
  10. class Derived1 : public Base
  11. {
  12.   public:
  13.   	Derived1(int) {}
  14.     virtual ~Derived1(void){}
  15. };
  16.  
  17. class Derived2 : public Base
  18. {
  19.   public:
  20.     virtual ~Derived2(void){}
  21. };
  22.  
  23.  
  24. namespace detail {
  25. template <class T, class Tuple, std::size_t... I>
  26. constexpr T make_from_tuple_impl( Tuple&& t, std::index_sequence<I...> )
  27. {
  28.   return T(std::get<I>(std::forward<Tuple>(t))...);
  29. }
  30.  
  31. template <class T, class Tuple>
  32. constexpr T make_from_tuple( Tuple&& t )
  33. {
  34.     return detail::make_from_tuple_impl<T>(std::forward<Tuple>(t),
  35.         std::make_index_sequence<std::tuple_size<std::decay_t<Tuple>>::value>{});
  36. }
  37.  
  38. template<typename... Args>
  39. struct DefferedConstruct {
  40. 	std::tuple<Args&...> args_tuple;
  41.  
  42. 	template<typename T>
  43. 	operator T*() {
  44. 		return new T(make_from_tuple<T>(
  45. 			args_tuple
  46. 		));
  47. 	}
  48. };
  49.  
  50. } // namespace detail
  51.  
  52. template<typename... Args>
  53. auto newObject(Args&&... args) -> detail::DefferedConstruct<Args...> {
  54. 	return detail::DefferedConstruct<Args...>{
  55. 		std::forward_as_tuple(args...)
  56. 	};
  57. }
  58.  
  59. int main()
  60. {
  61. 	    // compiler picks the right newObject function according to the parameter type
  62.     Derived1 *p1 = newObject(1);
  63.     Derived2 *p2 = newObject();
  64.  
  65.     delete p1;
  66.     delete p2;
  67. }
Success #stdin #stdout 0s 16064KB
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https://ideone.com/ilP0gq
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
secret

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