【C#设计模式(21)——状态模式(State Pattern)】

前言

状态模式:在对象内部发生改变时改变其行为，使得对象在不同的状态下具有不同的行为表现。

代码

 #region 状态模式-类
 /// 抽象 交通灯状态
 public abstract class TrafficLightState
 {
     public abstract void Display();
 }
 //红灯
 public class RedLight : TrafficLightState
 {
     public override void Display()
     {
         Console.WriteLine("红灯停");
     }
 }
 //绿灯
 public class GreenLight : TrafficLightState
 {
     public override void Display()
     {
         Console.WriteLine("绿灯行");
     }
 }
 //黄灯
 public class YellowLight : TrafficLightState
 {
     public override void Display()
     {
         Console.WriteLine("黄灯等待");
     }
 }
 //交通灯上下文
 public class TrafficLightContext
 {
     private TrafficLightState trafficLight;

     public TrafficLightContext()
     {
         trafficLight = new RedLight();
     }
     public void SetTrafficLightState(TrafficLightState trafficLight)
     {
         this.trafficLight = trafficLight;
     }
     public void Display()
     {
         trafficLight.Display();
     }
 }
 #endregion

 #region 状态模式-枚举
 //交通灯状态枚举
 public enum TrafficLightEnum
 {
     Red,
     Green,
     Yellow
 }
 //交通灯枚举状态显示设置类
 public class TrafficLightEnumState
 {
     private TrafficLightEnum state;
     public void SetState(TrafficLightEnum state)
     {
         this.state = state;
     }
     public void Display()
     {
         switch (state)
         {
             case TrafficLightEnum.Red:
                 Console.WriteLine("红灯停");
                 break;
             case TrafficLightEnum.Green:
                 Console.WriteLine("绿灯行");
                 break;
             case TrafficLightEnum.Yellow:
                 Console.WriteLine("黄灯等待");
                 break;
         }
     }
 }
 //交通灯上下文（枚举设置）
 public class TrafficLightEnumContext
 {
     private TrafficLightEnumState trafficLight;
     public TrafficLightEnumContext()
     {
         trafficLight = new TrafficLightEnumState();
         trafficLight.SetState(TrafficLightEnum.Red);
     }
     public void SetTrafficLightState(TrafficLightEnum state)
     {
         trafficLight.SetState(state);
     }
     public void Display()
     {
         trafficLight.Display();
     }
 }
 #endregion


/*
 * 行为型模式：Behavioral Pattern
 * 状态模式：State Pattern
 */
internal class Program
{
    /*
     * 行为型模式：Behavioral Pattern
     * 状态模式：State Pattern
     */
    static void Main(string[] args)
    {
        //类模式
        Console.WriteLine("类模式......");
        TrafficLightContext trafficLight = new TrafficLightContext();
        trafficLight.Display();
        trafficLight.SetTrafficLightState(new GreenLight());
        trafficLight.Display();
        trafficLight.SetTrafficLightState(new YellowLight());
        trafficLight.Display();

        //枚举模式
        Console.WriteLine("枚举模式......");
        TrafficLightEnumContext trafficLightEnumContext = new TrafficLightEnumContext();
        trafficLightEnumContext.Display();
        trafficLightEnumContext.SetTrafficLightState(TrafficLightEnum.Green);
        trafficLightEnumContext.Display();
        trafficLightEnumContext.SetTrafficLightState(TrafficLightEnum.Yellow);
        trafficLightEnumContext.Display();

        Console.ReadLine();
    }
}

运行结果