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  1. #include <iostream>
  2. #include <string>
  3. #include <typeinfo>
  4. #include <unordered_map>
  5. #include <functional>
  6. #include <typeindex>
  7. #include <cassert>
  8.  
  9. class Renderer;
  10. struct Renderable { virtual ~Renderable() {} };
  11. struct SelfRenderable : Renderable {
  12.     virtual void Render(Renderer& render) = 0;
  13. };
  14. class Renderer {
  15. public:
  16.     std::unordered_map<std::type_index, std::function<void(Renderer& renderer, const Renderable& renderable)>> rendering_functions;
  17.     void Render(Renderable& renderable) {
  18.         if (rendering_functions.find(typeid(renderable)) != rendering_functions.end())
  19.             return rendering_functions[typeid(renderable)](*this, renderable);
  20.         if (auto self = dynamic_cast<SelfRenderable*>(&renderable))
  21.             return self->Render(*this);
  22.         assert(false);
  23.     }
  24.     template<typename T, typename F> void AddRenderingFunction(F f) {
  25.         rendering_functions[typeid(T)] = [f](Renderer& renderer, const Renderable& renderable) {
  26.             return f(renderer, static_cast<const T&>(renderable));
  27.         };
  28.     }
  29.     void RenderText(std::string text) { 
  30.     	std::cout << text;
  31.     }
  32. };
  33. struct Player : Renderable {
  34.     std::string name;
  35. };
  36. int main() {
  37.     Renderer r;
  38.     Player p;
  39.     p.name = "Hello, World!";
  40.     r.AddRenderingFunction<Player>([](Renderer& rend, const Player& p) {
  41.         rend.RenderText(p.name);
  42.     });
  43.     r.Render(p);
  44. }
Success #stdin #stdout 0s 3432KB
comments (?)
stdin 
Standard input is empty
stdout 
Hello, World!
https://ideone.com/jJqCJh
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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