1 class CSubject;
 2 //观察者
 3 class CObserver
 4 {
 5 public:
 6     CObserver(){}
 7     virtual ~CObserver(){}
 8     virtual void Update(CSubject* pSubject) = 0;
 9 };
10 
11 //目标即主题，可理解为由于本对象变化导致其他对象跟随变化
12 class CSubject
13 {
14 public:
15     void Attach(CObserver* pO)
16     {
17         _ls.push_back(pO);
18     }
19     void Detach(CObserver* pO)
20     {
21         _ls.remove(pO);
22     }
23     void Notify()
24     {
25         for (list<CObserver*>::iterator it=_ls.begin();it!=_ls.end();it++)
26         {
27             (*it)->Update(this);
28         }
29     }
30 private:
31     list<CObserver*> _ls;
32 };
33 
34 //猫为观察者
35 class CCat:public CObserver
36 {
37 public:
38     CCat(){}
39     virtual ~CCat(){}
40     virtual void Update(CSubject* pSubject){
41         Say();
42     }
43     void Say()
44     {
45         printf("猫叫了\r\n");
46     }
47 };
48 
49 //人为观察者
50 class CPerson:public CObserver
51 {
52     public:
53         CPerson(){}
54         virtual ~CPerson(){}
55 
56     virtual void Update(CSubject* pSubject){
57         Say();
58     }
59     void Say()
60     {
61         printf("人醒了\r\n");
62     }
63 };
64 
65 //老鼠为主题
66 class CMouse:public CSubject
67 {
68 public:
69 
70     void Say()
71     {
72         printf("老鼠叫了\r\n");
73         Notify();
74     }
75 };

 1 int _tmain(int argc, _TCHAR* argv[])
 2 {
 3 
 4     //老鼠跑猫叫主人醒
 5     CMouse* pMouse = new CMouse();
 6     CCat* pCat = new CCat();
 7     CPerson* pPerson = new CPerson();
 8 
 9     pMouse->Attach(pCat);
10     pMouse->Attach(pPerson);
11     pMouse->Say();
12 　　
13     return 0;
14 }

 1 int _tmain(int argc, _TCHAR* argv[])
 2 {
 3 
 4     //老鼠跑猫叫主人醒
 5     CMouse* pMouse = new CMouse();
 6     CCat* pCat = new CCat();
 7     CPerson* pPerson = new CPerson();
 8 
 9     pMouse->Attach(pCat);
10     pMouse->Attach(pPerson);
11     pMouse->Say();
12 
13     //对称美，但是如此麻烦，还有其他解决方法吗
14     pMouse->Detach(pCat);
15     pMouse->Detach(pPerson);
16     delete pPerson;
17     delete pCat;
18     delete pMouse;
19     
20 
21     return 0;
22 }