狀態模式(State)

• 當一個物件的內在狀態改變時允許改變其行為，這個物件看起來像是改變了其類別。
• 主要解決的是，當控制一個物件狀態轉換的條件運算式過於複雜時，把狀態判斷邏輯表示不同狀態的一系列類別當中，可以把複雜的判斷邏輯簡化。

using System;

namespace DPExample
{
 class Work
 {
  private int hour;
  public int Hour {
   get { return hour; }
   set { hour = value; }
  }

  private bool finish = false;
  public bool TaskFinished {
   get { return finish; }
   set { finish = value; }
  }

  private State current;

  public void SetState(State s)
  {
   current = s;
  }

  public void WriteProgram()
  {
   current.Write (this);
  }

  public Work()
  {
   current = new ForenoonState();
  }
 }

 abstract class State
 {
  public abstract void Write(Work w);
 }

 class ForenoonState : State
 {
  public override void Write (Work w)
  {
   if (w.Hour < 12)
    Console.WriteLine ("當時時間：{0}點 上午工作，精神百倍", w.Hour);
   else {
    w.SetState (new NoonState ());
    w.WriteProgram();
   }
  }
 }

 class NoonState : State
 {
  public override void Write (Work w)
  {
   if (w.Hour < 13)
    Console.WriteLine ("當時時間：{0}點 餓了，午飯；覺的睏，午休", w.Hour);
   else {
    w.SetState (new AfternoonState());
    w.WriteProgram();
   }
  }
 }

 class AfternoonState : State
 {
  public override void Write (Work w)
  {
   if (w.Hour < 17)
    Console.WriteLine ("當時時間：{0}點 下午狀態還不錯，繼續努力", w.Hour);
   else {
    w.SetState (new EveningState());
    w.WriteProgram();
   }
  }
 }

 class EveningState : State
 {
  public override void Write (Work w)
  {
   if (w.TaskFinished) {
    w.SetState (new RestState ());
    w.WriteProgram ();
   } else {
    if (w.Hour < 21)
     Console.WriteLine ("當時時間：{0}點 加班哦，疲累至極", w.Hour);
    else
    {
     w.SetState (new SleepingState());
     w.WriteProgram();
    }
   }
  }
 }

 class SleepingState : State
 {
  public override void Write(Work w)
  {
   Console.WriteLine ("當時時間：{0}點 不行了，睡著了", w.Hour);
  }
 }

 class RestState : State
 {
  public override void Write(Work w)
  {
   Console.WriteLine ("當時時間：{0}點 下班回家了", w.Hour);
  }
 }
}