c++设计模式之观察者模式

观察者模式，有时我们又称为发布模式，当一个基类的状态（如某个属性）改变后，将会通知所有继承它的类的状态进行改变。

#include <iostream>
#include <list>
#include <numeric>
#include <algorithm>
using namespace std;

class ObserBase;

//base class of earth
class EarthBase
{
public:
 virtual void attach(ObserBase *o)=0;
 virtual void change()=0;
 virtual void setWeather(string str)=0;
 virtual string getWeather()=0;
};

//base class of observer
class ObserBase
{
public:
 virtual string getName()=0;
 virtual void update(EarthBase *s)=0;
 virtual void changeWeather(string weather)=0;
};

//earth class
class Earth:public EarthBase
{
private:
 string weather;
 std::list<ObserBase*> l;
public:
 Earth()
 {
 };
void attach(ObserBase *o)
{
 this->l.push_back(o);
};
void change()
{
 for(std::list<ObserBase*>::iterator it=l.begin();it!=l.end();++it)
 {
  (*it)->update(this);
 }
};
void setWeather(string str)
{
 this->weather=str;
 change();
};
string getWeather()
{
 return this->weather;
};
};

//oberver class, or satellite
class Observer:public ObserBase
{
private:
 string name;
 EarthBase* sub;
public:
 Observer(string str)
 {
  name=str;
 };
 Observer(string str,EarthBase* sub_)
 {
  name=str;
  sub = sub_;
  sub->attach(this);
 };
 string getName()
 {
  return name;
 };
 void update(EarthBase *s)
 {
  cout<<this->getName()+ " " + s->getWeather()<<endl;
 };
 void changeWeather(string weather)
 {
  sub->setWeather(weather);
 }
};

int main(int argc, char *argv[]) 
{
 Earth e;
 Observer *s1 = new Observer("风云一号");
 Observer *s2 = new Observer("风云二号");
 Observer *s3 = new Observer("风云三号");
 Observer *s4 = new Observer("风云四号");
 Observer *s5 = new Observer("风云五号",&e);
 e.attach(s1);
 e.attach(s2);
 e.attach(s3);
 e.attach(s4);
 e.setWeather("fine");
 s5->changeWeather("bad weather!!");
 return 0;
}