观察者模式

  1 #include <iostream>
  2 #include <string>
  3 #include <list>
  4 using namespace std;
  5 
  6 class Observer;
  7 
  8 class Subject
  9 {
 10 protected:
 11     list<Observer*> observers;
 12 public:
 13     string action;
 14 public:
 15     virtual void attach(Observer*) = 0;
 16     virtual void detach(Observer*) = 0;
 17     virtual void notify() = 0;
 18 };
 19 
 20 class Observer
 21 {
 22 protected:
 23     string name;
 24     Subject *sub;
 25 public:
 26     Observer(string name, Subject *sub)
 27     {
 28         this->name = name;
 29         this->sub = sub;
 30     }
 31     string getName()
 32     {
 33         return name;
 34     }
 35     virtual void update() = 0;
 36 };
 37 
 38 class StockObserver : public Observer
 39 {
 40 public:
 41     StockObserver(string name, Subject *sub) : Observer(name, sub)
 42     {
 43     }
 44     void update();
 45 };
 46 
 47 void StockObserver::update()
 48 {
 49     cout << name << " 收到消息：" << sub->action << endl;
 50     if (sub->action == "梁所长来了!")
 51     {
 52         cout << "我马上关闭股票，装做很认真工作的样子！" << endl;
 53     }
 54 }
 55 
 56 class NBAObserver : public Observer
 57 {
 58 public:
 59     NBAObserver(string name, Subject *sub) : Observer(name, sub)
 60     {
 61     }
 62     void update();
 63 };
 64 
 65 void NBAObserver::update()
 66 {
 67     cout << name << " 收到消息：" << sub->action << endl;
 68     if (sub->action == "梁所长来了!")
 69     {
 70         cout << "我马上关闭NBA，装做很认真工作的样子！" << endl;
 71     }
 72 }
 73 
 74 class Secretary : public Subject
 75 {
 76     void attach(Observer *observer)
 77     {
 78         observers.push_back(observer);
 79     }
 80     void detach(Observer *observer)
 81     {
 82         list<Observer *>::iterator iter = observers.begin();
 83         while (iter != observers.end())
 84         {
 85             if ((*iter) == observer)
 86             {
 87                 cout << "erase:" << observer->getName() << endl;
 88                 observers.erase(iter++);
 89             }
 90             else
 91             {
 92                 ++iter;
 93             }
 94         }
 95     }
 96     void notify()
 97     {
 98         list<Observer *>::iterator iter = observers.begin();
 99         while (iter != observers.end())
100         {
101             (*iter)->update();
102             ++iter;
103         }
104     }
105 };
106 
107 
108 int main()
109 {
110     Subject *dwq = new Secretary();
111 
112     Observer *xs = new NBAObserver("xiaoshuai", dwq);
113     Observer *zy = new NBAObserver("zouyue", dwq);
114     Observer *lm = new StockObserver("limin", dwq);
115 
116     dwq->attach(xs);
117     dwq->attach(zy);
118     dwq->attach(lm);
119 
120     dwq->action = "去吃饭了！";
121     dwq->notify();
122     cout << endl;
123 
124     dwq->action = "梁所长来了!";
125     dwq->notify();
126 
127     dwq->detach(lm);
128     dwq->detach(zy);
129     dwq->detach(xs);
130 
131     return 0;
132 }