详解C++设计模式编程中对状态模式的运用

namespace State_DesignPattern
 {
   using System;

   abstract  class State 
   {
     protected  string strStatename;    

     abstract  public  void Pour();
     // do something state-specific here 
   } 
 
   class OpenedState : State 
   {    
     public OpenedState ()
     {
      strStatename =  " Opened " ;
    } 
     override  public  void Pour()
     {
      Console.WriteLine( " pouring " );
      Console.WriteLine( " pouring " );
      Console.WriteLine( " pouring " );
    } 
  } 
  
   class ClosedState : State 
   {    
     public ClosedState()
     {
      strStatename =  " Closed " ;
    } 
     override  public  void Pour()
     {
      Console.WriteLine( " ERROR - bottle is closed - cannot pour " );
    } 
  } 
 
   class ContextColaBottle 
   {
     public  enum BottleStateSetting {
      Closed,
      Opened
    } ;

     // If teh state classes had large amounts of instance data,
     // we could dynamically create them as needed - if this demo
     // they are tiny, so we just create them as data members 
     OpenedState openedState =  new OpenedState();
    ClosedState closedState =  new ClosedState();

     public ContextColaBottle ()
     {
       // Initialize to closed 
       CurrentState = closedState;
    } 
 
     private State CurrentState;
    
     public  void SetState(BottleStateSetting newState)
     {
       if (newState == BottleStateSetting.Closed)
       {
        CurrentState = closedState;
      } 
       else 
       {
        CurrentState = openedState;
      } 
    } 
 
     public  void Pour()
     {
      CurrentState.Pour();
    }   
  } 
 
    ///  <summary> 
   ///   Summary description for Client.
   ///  </summary> 
   public  class Client
   {
     public  static  int Main( string [] args)
     {
      ContextColaBottle contextColaBottle =  new ContextColaBottle();

      Console.WriteLine( " initial state is closed " );

      Console.WriteLine( " Now trying to pour " );
       contextColaBottle.Pour();

      Console.WriteLine( " Open bottle " );
      contextColaBottle.SetState(ContextColaBottle.BottleStateSetting.Opened);

      Console.WriteLine( " Try to pour again " );
      contextColaBottle.Pour();

       return  0 ;
    } 
  } 
}