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  1. #include <iostream>
  2. #include <type_traits>
  3. #include <utility>
  4. #include <memory>
  5. using namespace std;
  6.  
  7. class Base
  8. {
  9. public:
  10. 	enum
  11. 	{
  12. 		BaseClass,
  13. 		Derived1Class,
  14. 		Derived2Class
  15. 	};
  16.  
  17. 	Base() {}
  18. 	~Base() {}
  19.  
  20. 	void printInfo() {std::cout << m_classType << std::endl;}
  21.  
  22. 	template<typename T, typename ... Args>
  23. 	static typename std::enable_if<std::is_base_of<Base, T>::value, std::unique_ptr<T>>::type create(Args ... args)
  24. 	{
  25. 		std::unique_ptr<T> result(new T(args...));
  26. 		result->initializeImpl();
  27. 		return result;
  28. 	}
  29.  
  30. protected:
  31. 	int m_classType;
  32.  
  33. 	virtual void initialize()
  34. 	{
  35. 		m_classType = BaseClass;
  36. 	}
  37.  
  38. private:
  39. 	void initializeImpl()
  40. 	{
  41. 		initialize();
  42. 	}
  43. };
  44.  
  45. class Derived1 : public Base
  46. {
  47. public:
  48. 	Derived1()
  49. 	{
  50. 		;
  51. 	}
  52.  
  53. private:
  54. 	void initialize() {m_classType = Derived1Class;}
  55. };
  56.  
  57. class Derived2 : public Base
  58. {
  59. public:
  60. 	Derived2()
  61. 	{
  62. 		;
  63. 	}
  64.  
  65. private:
  66. 	void initialize() {m_classType = Derived2Class;}
  67. };
  68.  
  69. class Derived3 : public Base
  70. {
  71. public:
  72. 	Derived3(int a) : m_type(a)
  73. 	{
  74. 		;
  75. 	}
  76.  
  77. private:
  78. 	int m_type;
  79.  
  80. 	void initialize() {m_classType = m_type;}
  81. };
  82.  
  83. class Derived4
  84. {
  85. public:
  86. 	Derived4(int a) : m_type(a)
  87. 	{
  88. 		;
  89. 	}
  90.  
  91. private:
  92. 	int m_type;
  93.  
  94. 	void initialize() {;}
  95. };
  96.  
  97. int main() {
  98. 	auto c1 = Base::create<Derived1>();
  99. 	auto c2 = Base::create<Derived2>();
  100. 	auto c3 = Base::create<Derived3>(10);
  101. 	// auto c4 = Base::create<Derived4>(20);
  102.  
  103. 	c1->printInfo();
  104. 	c2->printInfo();
  105. 	c3->printInfo();
  106.  
  107. 	return 0;
  108. }
Success #stdin #stdout 0s 3428KB
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https://ideone.com/i8gbSZ
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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