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  1. #include <vector>
  2. #include <type_traits>
  3.  
  4. struct Parent { };
  5. struct A : Parent { };
  6. struct B : Parent { };
  7. struct C : Parent { };
  8. struct E : Parent { };
  9.  
  10. struct tag_none { };
  11. struct tag_A { };
  12. struct tag_B { };
  13. struct tag_C { };
  14.  
  15. template <typename T>
  16. struct component_tag { using type = tag_none; };
  17. template <>
  18. struct component_tag <A> { using type = tag_A; };
  19. template <>
  20. struct component_tag <B> { using type = tag_B; };
  21. template <>
  22. struct component_tag <C> { using type = tag_C; };
  23.  
  24. class D
  25. {
  26. public:
  27.     template <typename T>
  28.     void Store();
  29.  
  30. private:
  31.     void Store_impl(void*, tag_none);
  32.     void Store_impl(A* component, tag_A);
  33.     void Store_impl(B* component, tag_B);
  34.     void Store_impl(C* component, tag_C);
  35.  
  36.     A *mA;
  37.     B *mB;
  38.     C *mC;
  39.     std::vector<Parent*> mComponents;
  40. };
  41.  
  42. template <typename T>
  43. void D::Store()
  44. {
  45.     using originalType = std::decay_t<std::remove_pointer_t<T> >;
  46.     originalType* component = new originalType();
  47.  
  48.     Store_impl(component, typename component_tag<originalType>::type { });
  49.  
  50.     mComponents.push_back(component);
  51. }
  52.  
  53. void D::Store_impl(void*, tag_none)
  54. {
  55.     // do nothing
  56. }
  57.  
  58. void D::Store_impl(A* component, tag_A)
  59. {
  60.     mA = component;
  61. }
  62.  
  63. void D::Store_impl(B* component, tag_B)
  64. {
  65.     mB = component;
  66. }
  67.  
  68. void D::Store_impl(C* component, tag_C)
  69. {
  70.     mC = component;
  71. }
  72.  
  73.  
  74. int main()
  75. {
  76. 	A a;
  77. 	B b;
  78. 	C c;
  79. 	E e;
  80.  
  81. 	D obj;
  82.  
  83. 	obj.Store<A>();
  84. 	obj.Store<B>();
  85. 	obj.Store<C>();
  86.  
  87. 	obj.Store<E>();
  88. }
Success #stdin #stdout 0s 3464KB
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https://ideone.com/82LTEf
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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