3月 19 2015

观察者模式

观察者模式定义了对象之间的一对多依赖，这样一来，当一个对象改变状态时，它的所有依赖者都会收到通知并自动更新。

#include<vector>
#include<iostream>
#include<string>
using namespace std;
 
class Subject;

//观察者抽象类
class Observer{                    
public:
  virtual void update(Subject *base)=0;
protected:
  Subject * _subject;
};

//主题抽象类
class Subject{
private:
	//观察者容器
	vector<Observer *> _observer;  
public:
	//数据值，可以作为私有数据，然后定义一个借口去返回值，这里为了省事
	string msg;                        
	void regiObserver(Observer *obs){
	_observer.push_back(obs);
  }
  void deleObserver(Observer *obs){
	  vector<Observer *>::iterator it;
	  for(it = _observer.begin(); it != _observer.end(); it++){
		  if( *it == obs){
			  _observer.erase(it);
			  break;
		  }
	  }
	  
  }
  //通知所有的观察者
  void notify(){                
    vector<Observer *>::iterator it;
    for(it = _observer.begin(); it != _observer.end(); it++)
      (*it)->update(this);
  } 
      
};
//秘书
class SecretarySubject:public Subject{                
public:
	void set(string s){
		msg = s;
		notify();                                   
	}
};

//打游戏的员工
class Gamesobserver :public Observer{    
public:
  Gamesobserver(Subject *base):Observer(){
    _subject = base;
    _subject->regiObserver(this);
  }
  void update(Subject *base){
    msg = base->msg;
    display();
  }
  void display(){
    cout<<msg<<"，关闭游戏界面"<<endl;
  }
private:
  string msg;
};
//炒股票的员工
class StockObserver:public Observer{    
 public:
  StockObserver(Subject * base){
    _subject = base;
    _subject->regiObserver(this);
  }
  void update(Subject *base){
    msg = base->msg;
    display();
  }
   void display(){
    cout<<msg<<"，关闭炒股界面"<<endl;
  }
private:
  string msg;
};
 
int main()
{
  SecretarySubject * sec = new SecretarySubject;
  Gamesobserver * one = new Gamesobserver(sec);
  StockObserver * two = new StockObserver(sec);
  sec->set("老板来了");
  //因为发现打游戏，开除了one
  sec->deleObserver(one);
  sec->set("老板来了");
  return 0;
}