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  1. #include <iostream>
  2. #include <list>
  3.  
  4. template<typename T>
  5. class Observer {
  6. public:
  7. //private:
  8.     virtual void notify(const T& data) = 0;
  9. public:
  10.     virtual ~Observer() = default;
  11. };
  12.  
  13. template<typename T>
  14. class Subject {
  15. public:
  16.     void subscribe(Observer<T> *observer);
  17.     void unsubscribe(Observer<T> *observer);
  18.     virtual ~Subject() = default;
  19. protected:
  20.     void notify(const T& data);
  21. private:
  22.     std::list<Observer<T>*> observers;
  23. };
  24.  
  25. template<typename T>
  26. void Subject<T>::subscribe(Observer<T> *observer) {
  27.     this->observers.push_back(observer);
  28. }
  29.  
  30. template<typename T>
  31. void Subject<T>::unsubscribe(Observer<T> *observer) {
  32.     this->observers.remove(observer);
  33. }
  34.  
  35. template<typename T>
  36. void Subject<T>::notify(const T& data) {
  37.     for (const auto &observer: this->observers) {
  38.         observer->notify(data);
  39.     }
  40. }
  41.  
  42. struct MoveData{};
  43. struct SteerData{};
  44.  
  45. class Car : public Subject<MoveData>, public Subject<SteerData> {
  46. public:
  47.     void move() {
  48.         const MoveData moveData{};
  49.         this->Subject<MoveData>::notify(moveData);
  50.     }
  51.  
  52.     void steer() {
  53.         const SteerData steerData{};
  54.         this->Subject<SteerData>::notify(steerData);
  55.     }
  56. };
  57.  
  58. struct MoveDataObserver : Observer<MoveData>
  59. {
  60.     void notify(const MoveData&) override { std::cout << "MoveDataObserver\n"; }
  61. };
  62.  
  63. struct SteerDataObserver : Observer<SteerData>
  64. {
  65.     void notify(const SteerData&) override { std::cout << "SteerDataObserver\n"; }
  66. };
  67.  
  68. int main()
  69. {
  70.     Car car;
  71.     MoveDataObserver obs1;
  72.     SteerDataObserver obs2;
  73.     car.Subject<MoveData>::subscribe(&obs1);
  74.     car.Subject<SteerData>::subscribe(&obs2);
  75.     car.move();
  76.     car.steer();
  77. }
Success #stdin #stdout 0.01s 5268KB
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MoveDataObserver
SteerDataObserver
https://ideone.com/e2gjN8
language:
C++ (gcc 8.3)
created:
7 days ago
visibility:
public

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