主讲：李建忠

来源：

 

 

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 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:  }