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  1. #include <iostream>
  2. #include <set>
  3. using namespace std;
  4.  
  5. struct EventHandle {};
  6.  
  7. class Subject; 
  8. class Observer {
  9. public:
  10.     virtual void OnEvent(const EventHandle& h, Subject& affectedItem) = 0;
  11.     virtual ~Observer() {}  // virtual function ? => better foresee a virtual destructor
  12. };
  13.  
  14. class Subject {
  15. public:
  16.     void AddObserver(Observer* o) {
  17.         observers.insert(o);
  18.     }
  19.     void RemoveObserver(Observer* o) {
  20.         //observers.remove(o);
  21.     }
  22.     void Notify(const EventHandle& h, Subject& affectedItem) {
  23.         for (Observer* o : observers) {
  24.             o->OnEvent(h, affectedItem);
  25.         }
  26.     }
  27. private:
  28.     set<Observer*> observers;
  29. };
  30.  
  31. struct ConcreteObserverA : Observer {
  32.     void OnEvent(const EventHandle& h, Subject& affectedItem) override {
  33.     	cout<<"A:"<<&affectedItem<<endl;
  34.     }
  35.  
  36. };
  37. struct ConcreteObserverB : Observer {
  38.     void OnEvent(const EventHandle& h, Subject& affectedItem) override {
  39.     	cout<<"B:"<<&affectedItem<<endl;
  40.     }
  41. };
  42.  
  43. struct ConcreteSubjectSA : Subject { };
  44. struct ConcreteSubjectSB : Subject { };
  45.  
  46.  
  47. int main() {
  48. 	 ConcreteSubjectSA sa1;
  49. 	 ConcreteSubjectSB sb1; 
  50. 	 ConcreteObserverA a1; 
  51. 	 ConcreteObserverB b1; 
  52. 	 sa1.AddObserver(&a1);
  53. 	 sa1.AddObserver(&b1);
  54. 	 sb1.AddObserver(&b1);
  55. 	 sa1.Notify (EventHandle{}, sa1);
  56. 	 sb1.Notify (EventHandle{}, sb1);
  57.  
  58.  
  59.  
  60. 	// your code goes here
  61. 	return 0;
  62. }
Success #stdin #stdout 0s 3460KB
comments (?)
stdin 
Standard input is empty
stdout 
A:0xbfc64b80
B:0xbfc64b80
B:0xbfc64b98
https://ideone.com/tQrlhf
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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