详解设计模式中的Command命令模式及相关C++实现

namespace Bridge_DesignPattern
{
  using System;

  class Abstraction 
  {
    protected Implementation impToUse;

    public void SetImplementation(Implementation i)
    {
      impToUse = i;
    }

    virtual public void DumpString(string str)
    {
      impToUse.DoStringOp(str);          
    }
  }

  class DerivedAbstraction_One : Abstraction 
  {
    override public void DumpString(string str)
    {
      str += ".com";
      impToUse.DoStringOp(str);      
    }    
  }

  class Implementation 
  {
    public virtual void DoStringOp(string str)
    {
      Console.WriteLine("Standard implementation - print string as is");
      Console.WriteLine("string = {0}", str);
    }    
  }

  class DerivedImplementation_One : Implementation 
  {
    override public void DoStringOp(string str)
    {
      Console.WriteLine("DerivedImplementation_One - don't print string");
    }  
  }

  class DerivedImplementation_Two : Implementation 
  {
    override public void DoStringOp(string str)
    {
      Console.WriteLine("DerivedImplementation_Two - print string twice");
      Console.WriteLine("string = {0}", str);
      Console.WriteLine("string = {0}", str);
    }  
  }
  
  /// <summary>
  ///  Summary description for Client.
  /// </summary>
  public class Client
  {
    Abstraction SetupMyParticularAbstraction() 
    {
      // we localize to this method the decision which abstraction and
      // which implementation to use. These need to be decided 
      // somewhere and we do it here. All teh rest of the client 
      // code can work against the abstraction object. 
      Abstraction a = new DerivedAbstraction_One();
      a.SetImplementation(new DerivedImplementation_Two());
      return a;
    }

    public static int Main(string[] args)
    {     
      Client c = new Client();
      Abstraction a = c.SetupMyParticularAbstraction();
        
      // From here on client code thinks it is talking to the 
      // abstraction, and will not need to be changed as 
      // derived abstractions are changed. 

      // more client code using the abstraction goes here 
      // . . . 
      a.DumpString("Clipcode");

      return 0;
    }
  }
}