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  1. #include <functional>
  2. #include <iostream>
  3. #include <stdexcept>
  4. #include <vector>
  5.  
  6. class C { public: virtual ~C() = default; };
  7. class C0 : public C { public: void print() { std::cout << "C0\n"; } };
  8. class C1 : public C { public: void print() { std::cout << "C1\n"; } };
  9.  
  10.  
  11. class PrintCaller
  12. {
  13. public:
  14.     template <typename T>
  15.     std::size_t register_class()
  16.     {
  17.         m.push_back([](C* c) {
  18.             auto* p = dynamic_cast<T*>(c);
  19.             if (p) {
  20.                 p->print();
  21.             } else {
  22.                 throw std::runtime_error("Incorrect type");
  23.             }
  24.         });
  25.         return m.size() - 1;
  26.     }
  27.  
  28.     void print(std::size_t id, C* c) const {
  29.         if (id < m.size()) {
  30.             m[id](c);
  31.         } else {
  32.             throw std::runtime_error("invalid id");
  33.         }
  34.     }
  35.  
  36. private:
  37.     std::vector<std::function<void(C*)>> m;
  38. };
  39.  
  40.  
  41. int main()
  42. {
  43.     C0 c0;
  44.     C1 c1;
  45.  
  46.     PrintCaller p;
  47.  
  48.     std::size_t id1 = p.register_class<C1>();
  49.     std::size_t id0 = p.register_class<C0>();
  50.  
  51.     p.print(id0, &c0);
  52.     p.print(id1, &c1);
  53.     try {
  54.         p.print(id1, &c0);
  55.     } catch (std::exception& e) {
  56.         std::cout << e.what();
  57.     }
  58. }
  59.  
Success #stdin #stdout 0s 3276KB
comments (?)
stdin
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Standard input is empty
stdout
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C0
C1
Incorrect type
https://ideone.com/bM2jMk
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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