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  1.     #include <iostream>
  2. 	#include <memory>
  3. 	#include <vector>
  4.  
  5. 	class A;
  6. 	class B;
  7. 	class C;
  8. 	class Visitor
  9. 	{
  10. 	public:
  11. 		void visit(A&)
  12. 		{
  13. 			std::cout << "A" << std::endl;
  14. 		}
  15. 		void visit(B&)
  16. 		{
  17. 			std::cout << "B" << std::endl;
  18. 		}
  19. 		void visit(C&)
  20. 		{
  21. 			std::cout << "C" << std::endl;
  22. 		}
  23. 	};
  24.  
  25. 	class Base {
  26. 	public:
  27. 		virtual void accept(Visitor& v) = 0;
  28. 	};
  29. 	class A : public Base{
  30. 	public:
  31. 		void accept(Visitor& v) override
  32. 		{
  33. 			v.visit(*this);
  34. 		}
  35. 	};
  36. 	class B : public Base{
  37. 	public:
  38. 		void accept(Visitor& v) override
  39. 		{
  40. 			v.visit(*this);
  41. 		}
  42. 	};
  43. 	class C : public Base{
  44. 	public:
  45. 		void accept(Visitor& v) override
  46. 		{
  47. 			v.visit(*this);
  48. 		}
  49. 	};
  50.  
  51. 	class CollectionOfBase
  52. 	{
  53. 	public:
  54. 		void add (std::shared_ptr<Base> item){m_items.push_back(item);}
  55. 		std::vector<std::shared_ptr<Base>> const& getItems() const {return m_items;}
  56.  
  57. 	private:
  58. 		std::vector<std::shared_ptr<Base>> m_items;
  59. 	};
  60.  
  61.     int main()
  62. 	{
  63. 		using namespace std;
  64.  
  65. 		CollectionOfBase collection;
  66.  
  67. 		collection.add(make_shared<A>());
  68. 		collection.add(make_shared<A>());
  69. 		collection.add(make_shared<C>());
  70. 		collection.add(make_shared<B>());
  71.  
  72. 		Visitor v;
  73. 		for (auto const& x : collection.getItems())
  74. 		{
  75. 			x->accept(v);
  76. 		}
  77. 		/*
  78. 		The desired output of this loop should be:
  79.  
  80. 		A
  81. 		A
  82. 		C
  83. 		B
  84.  
  85. 		*/
  86.  
  87. 		return 0;
  88. 	}
  89.  
  90.  
Success #stdin #stdout 0s 15248KB
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Standard input is empty
stdout
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A
A
C
B
https://ideone.com/2oT5S2
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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