C#中提供了IObservable<T>接口和IObserver<T>接口來實現觀察者模式,IObservable<T>至關於Subject(主題)接口,下面咱們就以代嗎來講明下如何利用.net框架提供的觀察者模式接口。框架
WeatherData類包含氣溫,溼度,氣壓等屬性。ide
class WeatherData { /// <summary> /// 氣溫 /// </summary> public string temperature { get; set; } /// <summary> /// 溼度 /// </summary> public string humility { get; set; } /// <summary> /// 氣壓 /// </summary> public string pressure { get; set; } }
WeatherDataPublisher類實現了IObservable接口,實現了Subscribe訂閱方法。this
class WeatherDataPublisher : IObservable<WeatherData> { List<IObserver<WeatherData>> observers = new List<IObserver<WeatherData>>(); /// <summary> /// 訂閱主題,將觀察者添加到列表中 /// </summary> /// <param name="observer"></param> /// <returns></returns> public IDisposable Subscribe(IObserver<WeatherData> observer) { observers.Add(observer); return new Unsubscribe(this.observers, observer); } /// <summary> /// 取消訂閱類 /// </summary> private class Unsubscribe : IDisposable { List<IObserver<WeatherData>> observers; IObserver<WeatherData> observer; public Unsubscribe(List<IObserver<WeatherData>> observers , IObserver<WeatherData> observer) { this.observer = observer; this.observers = observers; } public void Dispose() { if (this.observers != null) { this.observers.Remove(observer); } } } /// <summary> /// 通知已訂閱的觀察者 /// </summary> /// <param name="weatherData"></param> private void Notify(WeatherData weatherData) { foreach (var observer in observers) { observer.OnNext(weatherData); } } /// <summary> /// 接收最新的天氣數據 /// </summary> /// <param name="weatherData"></param> public void ReciveNewData(WeatherData weatherData) { Notify(weatherData); } }
下面咱們創建一個抽象類WeatherDisplayBase實現了IObserver接口,全部的天氣展現板(觀察者)繼承這個抽象類,需實現OnNext方法,即接收到新數據推送後要進行的數據處理展現工做,而且可重寫OnCompleted,OnError方法。spa
abstract class WeatherDisplayBase : IObserver<WeatherData> { public virtual void OnCompleted() { } public virtual void OnError(Exception error) { } public abstract void OnNext(WeatherData value); }
CurrentConditionDisplay類爲當前天氣情況展現板,繼承WeatherDisplayBase抽象類,展現最新的天氣數據。.net
class CurrentConditionDisplay : WeatherDisplayBase { public override void OnNext(WeatherData value) { Console.WriteLine("------------------"); Console.WriteLine("當前天氣情況板"); Console.WriteLine(string.Format("溫度:{0}\n溼度:{1}\n氣壓:{2}", value.temperature, value.humility, value.pressure)); } }
StatisticsConditionDisplay類爲氣溫統計展現板,繼承WeatherDisplayBase抽象類,展現歷史最高溫度,最低溫度,平均溫度。code
class StatisticsConditionDisplay : WeatherDisplayBase { List<float> temperatures = new List<float>(); public override void OnNext(WeatherData value) { float temperature; if (float.TryParse(value.temperature, out temperature)) { temperatures.Add(temperature); } Console.WriteLine("------------------"); Console.WriteLine("溫度統計板"); Console.WriteLine(string.Format("平均溫度:{0}\n最高溫度:{1}\n最低溫度:{2}", temperatures.Average(), temperatures.Max(), temperatures.Min())); } }
使用方法orm
class Program { static void Main(string[] args) { WeatherDataPublisher publisher = new WeatherDataPublisher(); CurrentConditionDisplay currentDisplay=new CurrentConditionDisplay(); StatisticsConditionDisplay statisticsDisplay = new StatisticsConditionDisplay(); //訂閱當前天氣展現板 IDisposable currentDisplayUnsubscriber= publisher.Subscribe(currentDisplay); //訂閱氣溫統計展現板 IDisposable statisticsDisplayUnsubscriber = publisher.Subscribe(statisticsDisplay); for (int i = 0; ; i++) { WeatherData weatherData = new WeatherData(); Console.WriteLine("請輸入溫度,溼度,壓力"); string input = Console.ReadLine(); var array= input.Split(','); weatherData.temperature = array[0]; weatherData.humility = array[1]; weatherData.pressure = array[2]; Console.WriteLine(""); //將輸入的新的天氣數據傳給天氣數據發佈器 publisher.ReciveNewData(weatherData); Console.WriteLine("============================="); } } }