#ifndef WEATHERDATA_H_INCLUDED

 #define WEATHERDATA_H_INCLUDED

 #include <set>

 #include "Display.h"

 class WeatherData

 {

 public:

     void measurementsChanged();

     void registerObserver( Display *p_display );

     void removeObserver( Display *p_display );

 private:

     int getTemperature() { return ; }

     int getHumidity() { return ; }

     int getPressure() { return ; }

     std::set<Display *> m_p_displays;

 };

 #endif // WEATHERDATA_H_INCLUDED

 #include "WeatherData.h"

 void WeatherData::measurementsChanged()

 {

     for ( std::set<Display *>::iterator it = m_p_displays.begin(); it != m_p_displays.end(); it++ )

     {

         (*it)->update( getTemperature(), getHumidity(), getPressure() );

     }

 }

 void WeatherData::registerObserver( Display *p_display )

 {

     m_p_displays.insert( p_display );

 }

 void WeatherData::removeObserver( Display *p_display )

 {

     m_p_displays.erase( p_display );

 }

 #ifndef DISPLAY_H_INCLUDED

 #define DISPLAY_H_INCLUDED

 class Display

 {

 public:

     virtual void update( int temp, int humidity, int pressure ) = ;

 };

 #endif // DISPLAY_H_INCLUDED

 #ifndef CURRENTCONDITIONSDISPLAY_H_INCLUDED

 #define CURRENTCONDITIONSDISPLAY_H_INCLUDED

 #include <iostream>

 #include "Display.h"

 class CurrentConditionsDisplay : public Display

 {

 public:

     void update( int temp, int humidity, int pressure ) { std::cout << "CurrentConditionsDisplay " << temp << "-" << humidity << "-" << pressure << std::endl; }

 };

 #endif // CURRENTCONDITIONSDISPLAY_H_INCLUDED

 #ifndef STATISTICSDISPLAY_H_INCLUDED

 #define STATISTICSDISPLAY_H_INCLUDED

 #include <iostream>

 #include "Display.h"

 class StatisticsDisplay : public Display

 {

 public:

     void update( int temp, int humidity, int pressure ) { std::cout << "StatisticsDisplay " << temp << "-" << humidity << "-" << pressure << std::endl; }

 };

 #endif // STATISTICSDISPLAY_H_INCLUDED

 #ifndef FORCASTDISPLAY_H_INCLUDED

 #define FORCASTDISPLAY_H_INCLUDED

 #include <iostream>

 #include "Display.h"

 class ForcastDisplay : public Display

 {

 public:

     void update( int temp, int humidity, int pressure ) { std::cout << "ForcastDisplay " << temp << "-" << humidity << "-" << pressure << std::endl; }

 };

 #endif // FORCASTDISPLAY_H_INCLUDED

 #include "WeatherData.h"

 #include "CurrentConditionsDisplay.h"

 #include "StatisticsDisplay.h"

 #include "ForcastDisplay.h"

 int main()

 {

     WeatherData weather_data;

     CurrentConditionsDisplay current_conditions_display;

     StatisticsDisplay statistics_display;

     ForcastDisplay forcast_display;

     weather_data.registerObserver( &current_conditions_display );

     weather_data.registerObserver( &statistics_display );

     weather_data.registerObserver( &forcast_display );

     weather_data.measurementsChanged();

     weather_data.removeObserver( &statistics_display );

     weather_data.measurementsChanged();

     return ;

 }