Headfirst设计模式的C++实现——观察者模式(Observer)

WeatherData.h

 #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

WeatherData.cpp

 #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 );
 }

Display.h

 #ifndef DISPLAY_H_INCLUDED
 #define DISPLAY_H_INCLUDED

 class Display
 {
 public:
     virtual void update( int temp, int humidity, int pressure ) = ;
 };

 #endif // DISPLAY_H_INCLUDED

CurrentConditionsDisplay.h

 #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

StatisticsDisplay.h

 #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

ForcastDisplay.h

 #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

main.cpp

 #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 ;
 }