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  1. #include <iostream>
  2. #include <string>
  3. #include <vector>
  4. #include <memory>
  5.  
  6. class C;
  7. class D;
  8. class Visitor
  9. {
  10. 	public:
  11. 	virtual ~Visitor() {}
  12. 	virtual void visitC( C& c ) = 0;
  13. 	virtual void visitD( D& d ) = 0;
  14. };
  15.  
  16.  
  17. class B{
  18.     private: int a; int b;
  19.     public: B(const int _a, const int _b) : a(_a), b(_b){}
  20.     virtual void tell(){ std::cout << "BASE" << std::endl; }
  21.     virtual void Accept( Visitor& v ) = 0;
  22. };
  23.  
  24. class C : public B{
  25.     std::string s;
  26.     public: C(int _a, int _b, std::string _s) : B(_a, _b), s(_s){}
  27.     void tell() override { std::cout << "CHILD C" << std::endl; }
  28.     void CFunc() {std::cout << "Can be called only from C" << std::endl;}
  29.     virtual void Accept( Visitor& v ) { v.visitC( *this ); }
  30. };
  31.  
  32. class D : public B{
  33.     double d;
  34.     public: D(int _a, int _b, double _d) : B(_a, _b), d(_d){}
  35.     void tell() override { std::cout << "CHILD D" << std::endl; }
  36.     void DFunc() {std::cout << "Can be called only from D" << std::endl;}
  37.     virtual void Accept( Visitor& v ) { v.visitD( *this ); }
  38. };
  39.  
  40. int main() {
  41.     std::vector<std::unique_ptr<B>> v;
  42.  
  43.     v.push_back(std::make_unique<C>(1,2, "boom"));
  44.     v.push_back(std::make_unique<D>(1,2, 44.3));
  45.  
  46. 	class callFuncVisitor : public Visitor
  47. 	{
  48. 		public:
  49. 		callFuncVisitor() {}
  50.  
  51. 		virtual void visitC( C& c )
  52. 		{
  53. 			c.CFunc();
  54. 		}
  55. 		virtual void visitD( D& d )
  56. 		{
  57. 			d.DFunc();
  58. 		}
  59. 	};
  60.  
  61. 	callFuncVisitor visitor;
  62.     for(auto &el: v){
  63.         el->Accept(visitor);
  64.     }
  65.     return 0;
  66. }
Success #stdin #stdout 0s 3472KB
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Standard input is empty
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Can be called only from C
Can be called only from D
https://ideone.com/JshiO6
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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