HeadFirst设计模式---观察者模式 C#实现

三个接口：

interface DisplayElement
    {
        void Display();
    }
interface Observer
    {
        void Update(float temp, float humidity, float pressure);
    }
interface Subject
    {
        void RegisterObserver(Observer observer);
        void RemoveObserver(Observer observer);
        void NotifyObserver();
    }

气象站主体：

实现subject的接口

class WeatherData : Subject
    {
        List<Observer> observers;
        float temperature;
        float humidity;
        float pressure;

        public WeatherData()
        {
            observers = new List<Observer>();
        }

        /// <summary>
        /// 通知每个对象刷新数据
        /// </summary>
        public void NotifyObserver()
        {
            int count = observers.Count;
            for (int i = 0; i < count; i++)
            {
                observers[i].Update(temperature,humidity,pressure);
            }
        }
        /// <summary>
        /// 注册对象
        /// </summary>
        /// <param name="observer"></param>
        public void RegisterObserver(Observer observer)
        {
            observers.Add(observer);
        }
        /// <summary>
        /// 注销对象
        /// </summary>
        /// <param name="observer"></param>
        public void RemoveObserver(Observer observer)
        {
            int index = observers.IndexOf(observer);
            if (index >= 0)
            {
                observers.RemoveAt(index);
            }
        }
        void GetTemperature()
        {
            temperature = new Random().Next(0, 40);
        }
        void GetHumidity()
        {
            humidity = new Random().Next(0, 30);
        }
        void GetPressure()
        {
            pressure = new Random().Next(0, 100);
        }
        
        public void MeasurementsChanged()
        {
            NotifyObserver();
        }

        /// <summary>
        /// 获得新的数据，并通知所有对象
        /// </summary>
        public void SetMeasuresments()
        {
            GetTemperature();
            GetHumidity();
            GetPressure();
            MeasurementsChanged();
        }

    }

观察者：布告板

实现observer和displayElement接口

class CurrentConditionsDisplay : Observer, DisplayElement
    {
        float temperature;
        float humidity;
        float pressure;
        Subject weatherData;
        public CurrentConditionsDisplay(Subject weatherData)
        {
            this.weatherData = weatherData;
            weatherData.RegisterObserver(this);
        }
        public void Display()
        {
            Console.WriteLine(this.ToString()
                + " temperature:" + temperature.ToString()
                + " humidity:" + humidity.ToString()
                + " pressure:" + pressure.ToString());
        }

        public void Update(float temp, float humidity, float pressure)
        {
            this.temperature = temp;
            this.humidity = humidity;
            this.pressure = pressure;
            Display();
        }
    }

主函数调用

class Program
    {
        static void Main(string[] args)
        {
            WeatherData weatherData = new WeatherData();
            CurrentConditionsDisplay currentConditionsDisplay = new CurrentConditionsDisplay(weatherData);
            weatherData.SetMeasuresments();
            weatherData.SetMeasuresments();
            weatherData.RemoveObserver(currentConditionsDisplay);
            weatherData.SetMeasuresments();
            Console.ReadKey();
        }
    }

可以看到当主函数中把布告板注销后 再次获取数值的时候  并没有通知该布告板