Observer Pattern

 1 #ifndef _SUBJECT_H_
 2 #define _SUBJECT_H_
 3 
 4 #include <list>
 5 #include <string> 
 6 using namespace std;
 7 
 8 typedef string State;
 9 class Observer;
10 
11 class Subject 
12 { 
13 public: 
14     virtual ~Subject();
15     virtual void Attach(Observer* obv);
16     virtual void Detach(Observer* obv);
17     virtual void Notify();
18     virtual void SetState(const State& st) = 0;
19     virtual State GetState() = 0;
20 protected: 
21     Subject();
22 private: 
23     list<Observer* >* _obvs;
24 };
25 
26 class ConcreteSubject:public Subject 
27 { 
28 public: 
29     ConcreteSubject();
30     ~ConcreteSubject();
31     State GetState();
32     void SetState(const State& st);
33 protected:
34 private: 
35     State _st;
36 };
37 
38 #endif

 1 #include "Subject.h" 
 2 #include "Observer.h"
 3 #include <iostream> 
 4 #include <list> 
 5 
 6 using namespace std;
 7 typedef string state;
 8 
 9 Subject::Subject() 
10 { 
11     //****在模板的使用之前一定要new，创建 
12     _obvs = new list<Observer*>;
13 }
14 Subject::~Subject() 
15 {
16 
17 }
18 void Subject::Attach(Observer* obv) 
19 { 
20     _obvs->push_front(obv); 
21 }
22 void Subject::Detach(Observer* obv) 
23 { 
24     if (obv != NULL)
25         _obvs->remove(obv);
26 }
27 void Subject::Notify() 
28 {
29     list<Observer*>::iterator it;
30     it = _obvs->begin();
31     for (;it != _obvs->end();it++) 
32     { //关于模板和iterator的用法
33         (*it)->Update(this); 
34     } 
35 }
36 ConcreteSubject::ConcreteSubject()
37 { 
38     _st = ‘\0‘; 
39 }
40 ConcreteSubject::~ConcreteSubject() 
41 {
42 
43 } 
44 State ConcreteSubject::GetState() 
45 { 
46     return _st; 
47 }
48 void ConcreteSubject::SetState(const State& st) 
49 { 
50     _st = st; 
51 }

 1 #ifndef _OBSERVER_H_ 
 2 #define _OBSERVER_H_
 3 
 4 #include "Subject.h"
 5 #include <string> 
 6 
 7 using namespace std;
 8 typedef string State;
 9 
10 class Observer 
11 { 
12 public: 
13     virtual ~Observer();
14     virtual void Update(Subject* sub) = 0;
15     virtual void PrintInfo() = 0;
16 protected:
17     Observer();
18     State _st;
19 private:
20 };
21 
22 class ConcreteObserverA:public Observer 
23 { 
24 public: 
25     virtual Subject* GetSubject(); 
26     ConcreteObserverA(Subject* sub);
27     virtual ~ConcreteObserverA();
28 
29     //传入Subject作为参数，这样可以让一个View属于多个的Subject。
30     void Update(Subject* sub);
31 
32     void PrintInfo();
33 protected:
34 private: 
35     Subject* _sub;
36 };
37 
38 class ConcreteObserverB:public Observer 
39 { 
40 public: 
41     virtual Subject* GetSubject();
42     ConcreteObserverB(Subject* sub);
43     virtual ~ConcreteObserverB();
44 
45     //传入Subject作为参数，这样可以让一个View属于多个的Subject。
46     void Update(Subject* sub);
47 
48     void PrintInfo();
49 protected:
50 private: 
51     Subject* _sub;
52 };
53 
54 #endif

 1 #include "Observer.h" 
 2 #include "Subject.h"
 3 #include <iostream> 
 4 #include <string> 
 5 using namespace std;
 6 
 7 Observer::Observer() 
 8 { 
 9     _st = ‘\0‘;
10 }
11 Observer::~Observer() 
12 {
13 
14 } 
15 ConcreteObserverA::ConcreteObserverA(Subject* sub) 
16 { 
17     _sub = sub;
18     _sub->Attach(this);
19 }
20 ConcreteObserverA::~ConcreteObserverA() 
21 {
22     _sub->Detach(this);
23     if (_sub != 0) 
24     { 
25         delete _sub;
26     } 
27 }
28 Subject* ConcreteObserverA::GetSubject() 
29 { 
30     return _sub; 
31 }
32 void ConcreteObserverA::PrintInfo() 
33 { 
34     cout<<"ConcreteObserverA observer.... "<<_sub->GetState()<<endl; 
35 }
36 void ConcreteObserverA::Update(Subject* sub) 
37 { 
38     _st = sub->GetState();
39     PrintInfo();
40 }
41 ConcreteObserverB::ConcreteObserverB(Subject* sub) 
42 { 
43     _sub = sub;
44     _sub->Attach(this); 
45 }
46 ConcreteObserverB::~ConcreteObserverB() 
47 { 
48     _sub->Detach(this);
49     if (_sub != 0) 
50     { 
51         delete _sub; 
52     } 
53 }
54 Subject* ConcreteObserverB::GetSubject() 
55 {
56     return _sub; 
57 }
58 void ConcreteObserverB::PrintInfo() 
59 { 
60     cout<<"ConcreteObserverB observer.... "<<_sub->GetState()<<endl; 
61 }
62 void ConcreteObserverB::Update(Subject* sub) 
63 { 
64     _st = sub->GetState();
65     PrintInfo(); 
66 }

 1 #include "Subject.h" 
 2 #include "Observer.h"
 3 #include <iostream> 
 4 using namespace std;
 5 
 6 int main(int argc,char* argv[]) 
 7 { 
 8     ConcreteSubject* sub = new ConcreteSubject();
 9     Observer* o1 = new ConcreteObserverA(sub);
10     Observer* o2 = new ConcreteObserverB(sub);
11     sub->SetState("old");
12     sub->Notify();
13     sub->SetState("new"); //也可以由Observer调用
14     sub->Notify();
15     return 0; 
16 }