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  1. #include <iostream>
  2. #include <map>
  3.  
  4. class TypeRegistry {
  5. 	public:
  6. 		TypeRegistry() {
  7. 			counter = 0;
  8. 		}
  9.  
  10. 		template <typename T>
  11. 		int getTypeId() {
  12. 			static int id = -1;
  13.  
  14. 			if (id < 0) {
  15. 				id = counter++;
  16. 			}
  17.  
  18. 			return id;
  19. 		}
  20.  
  21. 		static TypeRegistry & getInstance() {
  22. 			static TypeRegistry t;
  23.  
  24. 			return t;
  25. 		}
  26.  
  27. 	private:
  28. 		int counter;
  29. };
  30.  
  31. class Foo {
  32. 	public:
  33. 		template <typename T>
  34. 		T & get() {
  35. 			std::map<int, void*>::iterator i;
  36. 			int id;
  37.  
  38. 			id = TypeRegistry::getInstance().getTypeId<T>();
  39. 			i = this->values.find(id);
  40.  
  41. 			if (i != this->values.end())
  42. 				return *(T*)i->second;
  43.  
  44. 			T *value = new T();
  45. 			this->values[id] = value;
  46. 			return *value;
  47. 		}
  48.  
  49. 		size_t size() const {
  50. 			return this->values.size();
  51. 		}
  52.  
  53. 	private:
  54. 		std::map<int, void*> values;
  55. };
  56.  
  57.  
  58.  
  59. int main()
  60. {
  61. 	Foo a, b;
  62.  
  63. 	a.get<int>() = 1;
  64. 	a.get<float>() = 3.14;
  65. 	b.get<int>() = 2;
  66. 	b.get<double>() = 3.14159;
  67. 	b.get<float>() = 1.23;
  68.  
  69. 	std::cout << "a<int> = " << a.get<int>() << std::endl; 
  70. 	std::cout << "a<float> = " << a.get<float>() << std::endl; 
  71. 	std::cout << "size of a = " << a.size() << std::endl; 
  72. 	std::cout << "b<int> = " << b.get<int>() << std::endl; 
  73. 	std::cout << "b<double> = " << b.get<double>() << std::endl; 
  74. 	std::cout << "b<float> = " << b.get<float>() << std::endl; 
  75. 	std::cout << "size of b = " << b.size() << std::endl;
  76.  
  77. 	a.get<int>()++;
  78. 	a.get<float>() += 3.14;
  79. 	b.get<int>() -= 2;
  80. 	b.get<double>() *= 3.14159;
  81. 	b.get<float>() /= 1.23;
  82.  
  83. 	std::cout << "a<int> = " << a.get<int>() << std::endl; 
  84. 	std::cout << "a<float> = " << a.get<float>() << std::endl; 
  85. 	std::cout << "size of a = " << a.size() << std::endl; 
  86. 	std::cout << "b<int> = " << b.get<int>() << std::endl; 
  87. 	std::cout << "b<double> = " << b.get<double>() << std::endl; 
  88. 	std::cout << "b<float> = " << b.get<float>() << std::endl; 
  89. 	std::cout << "size of b = " << b.size() << std::endl;
  90.  
  91. 	return 0;
  92. }
  93.  
  94.  
  95.  
Success #stdin #stdout 0s 3476KB
comments (?)
stdin 
Standard input is empty
stdout 
a<int> = 1
a<float> = 3.14
size of a = 2
b<int> = 2
b<double> = 3.14159
b<float> = 1.23
size of b = 3
a<int> = 2
a<float> = 6.28
size of a = 2
b<int> = 0
b<double> = 9.86959
b<float> = 1
size of b = 3
https://ideone.com/oPvexQ
language:
C++ (gcc 8.3)
created:
11 years ago
visibility:
public

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