patterns/observer/weather-info-events/observer.cs - A WeatherCenter (subject) and Temperature/Rain Watchers (observer) with events.

Lecture 6 - slide 20 : 20 Program 2

using System;
using System.Collections;

namespace Templates.Observer {

 // Delegate type:
 public delegate void 
    WeatherNotification(float temp, float rain, float pres);

 // An observer
 public class TemperatureWatcher {

   private float currentTemperature;
   private WeatherCenter mySubject;
   private string watcherName; 

   public TemperatureWatcher (WeatherCenter s, float initTemp, string name){
     mySubject = s;
     currentTemperature = initTemp;
     watcherName = name;
   }   

   public void TemperatureAlarm(float temp, float rain, float pres){
      currentTemperature = temp;
      Console.WriteLine(
           "Temperature watcher {1}: the temperature is now {0}.", 
           currentTemperature, watcherName);
   }
 }    

 public class RainWatcher {

   private float currentRainAmount;
   private WeatherCenter mySubject;
   private string watcherName; 

   public RainWatcher (WeatherCenter s, float initAmount, string name){
     mySubject = s;
     currentRainAmount = initAmount;
     watcherName = name;
   }      

   public void RainAlarm(float temp, float rain, float pres){
      currentRainAmount = rain;
      Console.WriteLine("Rain watcher {1}: Accumulated rain fall: {0}.", 
                         currentRainAmount, watcherName);
   }   
 }    

 // A subject
 public class WeatherCenter {

   private float temperature,
                 rainAmount,
                 airPressure;

   public WeatherCenter(float temp, float rain, float pres){
      temperature = temp;
      rainAmount = rain;
      airPressure = pres;
   }

   public void WeatherUpdate(float temp, float rain, float pres){
      float oldTemperature = this.temperature,
            oldRainAmount = this.rainAmount,
            oldAirPressure = this.airPressure;

      this.temperature = temp;
      this.rainAmount += rain;
      this.airPressure = pres;

      if (Math.Abs(oldTemperature - this.temperature) > 2.0F ||
          rain > 0.5F ||
          Math.Abs(oldAirPressure - this.airPressure) > 3.0F)
       this.Notify();
   }
        
   private event WeatherNotification weatherNotifier;

   public void AddNotifier(WeatherNotification n){
     weatherNotifier += n;
   }

   public void RemoveNotifier(WeatherNotification n){
     weatherNotifier -= n;
   }

   public void Notify(){
     weatherNotifier(temperature, rainAmount, airPressure);
   }

 }    


}