模式学习（1）：Decorator装饰者模式

 

学习（主要参考 刘艺 delphi模式编程）

概念：Decorator以对客户端透明的方式动态的为对象提供修饰等附加的功能。

使用时机：1、在不影响其他对象的情况下，动态透明的增加责任或功能到某一对象。

              2、这些功能可以随时添加或取消；

              3、为了增加大量的功能，而导致派生类激增，继承关系复杂而不现实时；累的定义被隐藏或定义不方便派生类的。

模式结构：1、抽象的部件：定义一个接口（类），可以动态附加在其他对象上。抽象虚拟类。(可理解为要实现的功能，当然是类中定义的方法)

                     TMethod:=class(TObject);

                            procedure XXX();virtual;Abstract;

                     end;

              2、具体的需要被修饰的部件：被修饰的（类）对象。

                     TSomething=class(TMethod);

                             procedure XXX();override;

              3、装饰者：定义与抽象部件（1）一致的接口（函数），维护一个到1的引用，以便修饰抽象部件对象的接口。

                    TDecorateSomething=class(TMethod); 

                               procedure XXX();override;                         

              4、具体装饰者：附加到2上，实现不同的功能效果。

                    TSomething臭美1=class(TDecorateSomething);procedure XXX();override;

                    TSomething臭美2=class(TDecorateSomething);procedure XXX();override;

 

类图：

此类图根据刘艺的例子使用modalmaker11制作。

View Code

  1 unit PicDecorator;
  2 
  3 interface
  4 
  5 uses Windows, Controls, Classes, SysUtils, Forms, Graphics, Dialogs, Jpeg,
  6   Extctrls, ComCtrls, Messages;
  7 
  8 type
  9   TPicShow = class(TObject)
 10   public
 11     procedure Display(AWoner: TForm; ImgFile: string); virtual; abstract;
 12   end;
 13 
 14   TPic = class(TPicShow)
 15   public
 16     procedure Display(AWoner: TForm; ImgFile: string); override;
 17   end;
 18 
 19   TDecoratedPic = class(TPicShow)
 20   private
 21     FComponent: TPicShow;
 22   public
 23     constructor Create(PicShow: TPicShow);
 24     procedure Display(AWoner: TForm; ImgFile: string); overload; override;
 25     // property Component: TPicShow read FComponent;
 26   end;
 27 
 28   TPicWithMusic = class(TDecoratedPic)
 29   public
 30     destructor Destroy; override;
 31     procedure AddMusic;
 32     procedure Display(AWoner: TForm; ImgFile: string); override;
 33   end;
 34 
 35   TPicWithFrame = class(TDecoratedPic)
 36   private
 37     FAddedFrame: Integer;
 38   public
 39     destructor Destroy; override;
 40     procedure Display(AWoner: TForm; ImgFile: string); override;
 41   end;
 42 
 43 implementation
 44 
 45 {
 46   ************************************* TPic *************************************
 47 }
 48 procedure TPic.Display(AWoner: TForm; ImgFile: string);
 49 var
 50   Img: TImage;
 51 begin
 52   Img := TImage.Create(AWoner);
 53   Img.Picture.LoadFromFile(ImgFile);
 54   Img.AutoSize := true;
 55   Img.Stretch := true;
 56   AWoner.Width := Img.Width + 32;
 57   AWoner.Height := Img.Height + 64;
 58   AWoner.Caption := ImgFile;
 59   Img.Left := 11;
 60   Img.Top := 13;
 61   Img.Parent := AWoner;
 62 end;
 63 
 64 {
 65   ******************************** TDecoratedPic *********************************
 66 }
 67 constructor TDecoratedPic.Create(PicShow: TPicShow);
 68 begin
 69   self.FComponent := PicShow;
 70 end;
 71 
 72 procedure TDecoratedPic.Display(AWoner: TForm; ImgFile: string);
 73 begin
 74   if FComponent <> nil then
 75   begin
 76     FComponent.Display(AWoner, ImgFile);
 77   end;
 78 end;
 79 
 80 {
 81   ******************************** TPicWithMusic *********************************
 82 }
 83 destructor TPicWithMusic.Destroy;
 84 begin
 85   // 结束播放，sndPlaySOund(nil,snd_noDefault);
 86   showmessage('Over Music');
 87   if FComponent <> nil then
 88     FComponent.Free;
 89 end;
 90 
 91 procedure TPicWithMusic.AddMusic;
 92 begin
 93   // 添加播放的音乐
 94   showmessage('add music');
 95 end;
 96 
 97 procedure TPicWithMusic.Display(AWoner: TForm; ImgFile: string);
 98 begin
 99   inherited Display(AWoner, ImgFile);
100   AddMusic;
101 end;
102 
103 {
104   ******************************** TPicWithFrame *********************************
105 }
106 destructor TPicWithFrame.Destroy;
107 begin
108   if FComponent <> nil then
109     FComponent.Free;
110 end;
111 
112 procedure TPicWithFrame.Display(AWoner: TForm; ImgFile: string);
113 var
114 FrmOut:TBevel;
115 FrmIn:TBevel;
116 begin
117 inherited Display(AWOner,imgfile);
118 FrmIn:=TBevel.Create(AWoner);
119 FrmIn.Parent:=AWoner;
120 frmin.Width:=AWoner.Width-30;
121 frmin.Height:=AWOner.Height-62;
122 frmin.Left:=10;
123 frmin.Top:=12;
124 frmin.Shape:=bsBox;
125 frmin.Style:=bsLowered;
126 
127 frmout:=TBevel.Create(AWOner);
128 Frmout.Parent:=AWoner;
129 frmout.Width:=AWoner.Width-18;
130 frmout.Height:=AWOner.Height-48;
131 frmout.Left:=4;
132 frmout.Top:=6;
133 frmout.Shape:=bsBox;
134 frmout.Style:=bsraised;
135 end;
136 
137 end.

View Code

 1 unit Unit3;
 2 
 3 interface
 4 
 5 uses
 6   Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
 7   Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ExtCtrls, Vcl.StdCtrls, Vcl.FileCtrl;
 8 
 9 type
10   TForm3 = class(TForm)
11     DirectoryListBox1: TDirectoryListBox;
12     DriveComboBox1: TDriveComboBox;
13     Edit1: TEdit;
14     Panel1: TPanel;
15     FileListBox1: TFileListBox;
16     FilterComboBox1: TFilterComboBox;
17     Button1: TButton;
18     Button2: TButton;
19     RadioGroup1: TRadioGroup;
20     Bevel1: TBevel;
21     Image1: TImage;
22     procedure Button1Click(Sender: TObject);
23     procedure Button2Click(Sender: TObject);
24     procedure Edit1KeyPress(Sender: TObject; var Key: Char);
25     procedure FileListBox1Click(Sender: TObject);
26   private
27     { Private declarations }
28     imgfilename:string;
29   public
30     { Public declarations }
31   end;
32 
33 var
34   Form3: TForm3;
35 
36 implementation
37 uses PicDecorator;
38 {$R *.dfm}
39 
40 procedure TForm3.Button1Click(Sender: TObject);
41 var
42  decopic:TPicShow;
43  currfrm:TForm;
44 begin
45  currfrm:=TForm.Create(nil);
46  case self.RadioGroup1.ItemIndex of
47  0: decopic:=TPicwithframe.Create(Tpic.Create);
48  1: decopic:=TPicwithMusic.Create(Tpic.Create);
49  2: ;
50  end;
51  try
52    decopic.Display(currfrm,imgfilename);
53    currfrm.ShowModal;
54 
55  finally
56    decopic.Free;
57    currfrm.Free;
58  end;
59 end;
60 
61 procedure TForm3.Button2Click(Sender: TObject);
62 begin
63   close;
64 end;
65 
66 procedure TForm3.Edit1KeyPress(Sender: TObject; var Key: Char);
67 begin
68   if key=#13 then
69   begin
70     filelistbox1.ApplyFilePath(edit1.Text);
71     key:=#0;
72   end;
73 end;
74 
75 procedure TForm3.FileListBox1Click(Sender: TObject);
76 var
77  fileExt:string[4];
78 begin
79  fileExt:=ansiUppercase(ExtractfileExt(filelistbox1.FileName));
80  self.Button1.Enabled:=false;
81  if (fileExt='.JPG') then
82  begin
83    self.Image1.Picture.LoadFromFile(filelistbox1.FileName);
84    imgfilename:=filelistbox1.FileName;
85    button1.Enabled:=true;
86  end;
87 
88 end;
89 
90 end.

代码为实现的例子。