C#面向对象设计模式纵横谈——15 Command命令模式

主讲：李建忠

来源：http://www.microsoft.com/china/msdn/events/webcasts/shared/webcast/consyscourse/CsharpOOD.aspx

 

 

   1:  //已经存在的，实现细节，低层实现

   2:  class Document

   3:  {

   4:      public void ShowText()

   5:      {

   6:          //...

   7:      }

   8:  }

   9:   

  10:  class Graphics

  11:  {

  12:      public void ShowGraphics()

  13:      {

  14:          //...

  15:      }

  16:  }

  17:   

  18:  //实现Command设计模式

  19:  public interface Command

  20:  {

  21:      public void Show();

  22:      public void Undo();

  23:      public void Redo();

  24:  }

  25:   

  26:  //具体化的命令对象——从抽象意义来讲，DocumentCommand表示一个行为

  27:  class DocumentCommand:Command

  28:  {

  29:      Document document;

  30:      public DocumentCommand(Document doc)

  31:      {

  32:          this.document=doc;

  33:      }

  34:   

  35:      public void Show()

  36:      {

  37:          document.ShowText();

  38:      }

  39:   

  40:      public void Undo()

  41:      {

  42:   

  43:      }

  44:   

  45:      public void Redo()

  46:      {

  47:   

  48:      }

  49:  }

  50:   

  51:  class GraphicCommand:Command

  52:  {

  53:   

  54:  }

  55:   

  56:  //应用程序主干，高层抽象

  57:  class Application

  58:  {

  59:      Stack<Command> stack;

  60:   

  61:      public void Show()

  62:      {

  63:          foreach(Command c in list)

  64:          {

  65:              c.show();

  66:          }

  67:      }

  68:   

  69:      public void Undo()

  70:      {

  71:          if(canUndo)

  72:          {

  73:              Command command=stack.pop();

  74:              command.Undo();

  75:   

  76:              undoList.Add(command);

  77:          }

  78:      }

  79:   

  80:      public void Redo()

  81:      {

  82:          if(canRedo)

  83:          {

  84:              Command command=undoList.pop();

  85:              command.Undo();

  86:          }

  87:      }

  88:  }