cpp 实现简单的观察者模式

 1 #include <iostream>
 2 #include <vector>
 3 #include <functional>
 4 #include <iomanip>
 5 #include <set>
 6 
 7 using namespace std;
 8 
 9 class Observer{
10 public:
11     void update(){
12         cout<<"update"<<endl;
13     }
14 };
15 class Subject{
16 public:
17     void regist(Observer *pobs){
18         pobs_set.insert(pobs);
19     }
20     void unregist(Observer *pobs){
21         pobs_set.erase(pobs);
22     }
23     void change(const int state){
24         this->state = state;
25         notify();
26     }
27 private:
28     void notify(){
29         for(auto po : this->pobs_set){
30             po->update();
31         }
32     }
33     multiset<Observer*> pobs_set;
34     int state;
35 };
36 int main()
37 {
38     Observer o1,o2,o3;
39     Subject sub;
40     sub.regist(&o1);
41     sub.regist(&o2);
42     sub.regist(&o3);
43 
44     sub.change(12);
45 
46     cout<<"----------------"<<endl;
47     sub.unregist(&o1);
48     sub.change(122);
49 
50 
51     return 0;
52 }