：观察者模式--Weather

#ifndef __WEATHER_H__
#define __WEATHER_H__
#include <list>
#include <iostream>
using namespace std;

class DisplayElement
{
public:
	DisplayElement(){}
	virtual ~DisplayElement(){}
	virtual void display(){}
};
class Subject;

class Observer
{
public:
	Observer(){}

	virtual ~Observer(){}

	virtual void update(float temp, float humidit, float pressure){}

};

class CurrentWeatherDisplay:public Observer, public DisplayElement
{
private:
	float temperature;
	float humidity;
	float pressure;
	Subject *weatherData;

public:
	CurrentWeatherDisplay(Subject *wd);

	virtual ~CurrentWeatherDisplay(){}

	virtual void CurrentWeatherDisplay::display()
	{
		std::cout << "This is Current" << temperature << "  " << humidity << " " << pressure << endl;
	}

	virtual void CurrentWeatherDisplay::update(float temp, float hum, float pres)
	{
		temperature = temp;
		humidity = hum;
		pressure = pres;
		display();
	}

};

#endif

#ifndef __SUBJECT_H__
#define __SUBJECT_H__
#include <list>
#include <iostream>
#include "Observer.h"

using namespace std;

class Subject
{
public:
	Subject(){}

	virtual ~Subject(){}

	virtual void registerObserver(Observer *obs){}

	virtual void removeObserver(Observer *obs){}

	virtual void notifyObserver(){}
};

class WeatherData : public Subject
{
private:
	std::list<Observer*>observer;
	float temperature;
	float humidity;
	float pressure;
public:
	WeatherData(){}
	virtual ~WeatherData(){}

	virtual void registerObserver(Observer *obs){	observer.push_back(obs);	}

	virtual void removeObserver(Observer *obs)	{	observer.remove(obs);}

	virtual void notifyObserver()
	{
		std:list<Observer *>::iterator it = observer.begin();
		for (; it != observer.end(); it++)
		{
			(*it)->update(temperature, humidity, pressure);
		}
	}

	void measurementsChanged(){	notifyObserver();}

	void setMeasurements(float temp, float hum, float pre)
	{
		temperature = temp;
		humidity = hum;
		pressure = pre;
		measurementsChanged();
	}
};

CurrentWeatherDisplay::CurrentWeatherDisplay(Subject *wd)
{
	weatherData = wd;
	weatherData->registerObserver(this);
}

#endif

#include <iostream>
#include "Subject.h"
using namespace std;
int main()
{
	WeatherData *wd = new WeatherData();
	CurrentWeatherDisplay * cu = new CurrentWeatherDisplay(wd);
	wd->setMeasurements(10, 20, 30);
	wd->setMeasurements(20, 40, 80);
	wd->setMeasurements(100, 200, 300);
	return 0;
}