《大话设计模式》之 装饰模式 Delphi实现

装饰模式：动态地给一个对象添加一些额外的职责。就增加功能来说，Decorator模式相比生成子类更为灵活。[GOF 《设计模式》]

这句话怎么理解？

一般来说，增加功能，一般有增加类本身的功能；另外一种是增加子类；但是现实中，靠增加子类来满足实际需求，是远远不够的，缺少灵活性；

装饰模式，它强调的要增加功能，但又不允许生产过多子类，那么该怎么实现呢？ 它的指导思想，是进行包裹，层次包裹。子类对象包裹父类对象，一层一层，功能就一层一层。

1.首先定义一个首先抽象类或接口；

2.定了两个继承抽象类或实现接口方法的类，一个是装饰类，一个一般类，装饰类，定义一个方法，接受父类型；

{

装饰模式，强调的功能逐渐一层层包裹。 本例子， 以西游记中，孙悟空的72般变化，话说当年，

悟空不远千里，拜师学艺，功夫是一天天长进。腾云驾雾，翻筋斗，变美女/树等，这些功夫，是

一一学会的。

抽象虚拟类，作为父类。

所有代码 均在 Delphi7 测试通过

}

unit Decorator;

interface

uses ComObj;

type

{基础类}

TMonkey = class(TObject)

private

FMonkey: TMonkey;

public

FGongFu: string;

procedure Operation; virtual;

procedure SetGongFuMonkey(Monkey: TMonkey);

procedure WriteLog;

end;

{无法术}

TFongFuNo = class(TMonkey)

public

procedure Operation; override;

end;

{腾云驾雾}

TGongFuKey = class(TMonkey)

public

procedure Operation; override;

end;

{翻筋斗}

TGongFuSomeRsault = class(TMonkey)

public

procedure Operation; override;

end;

{变树/美人}

TGongFuChange = class(TMonkey)

public

procedure Operation; override;

procedure AddOtherMethod;

end;

implementation

uses Unit1;

{ TGongFuKey }

procedure TGongFuKey.Operation;

begin

inherited;

FGongFu := '已经学会腾云驾雾之术';

WriteLog;

end;

{ TGongGuSomeRsault }

procedure TGongFuSomeRsault.Operation;

begin

inherited;

FGongFu := '已经学会翻跟斗';

WriteLog;

end;

{ TGongFuChange }

procedure TGongFuChange.AddOtherMethod;

begin

{增加其它方法}

end;

procedure TGongFuChange.Operation;

begin

inherited;

FGongFu := '已经变美女和变树';

WriteLog;

AddOtherMethod;

{......}

end;

{ TMonkey }

procedure TMonkey.SetGongFuMonkey(Monkey: TMonkey);

begin

FMonkey := Monkey;

end;

procedure TMonkey.Operation;

begin

if FMonkey <> nil then

FMonkey.Operation;

end;

procedure TMonkey.WriteLog;

begin

Form1.Memo1.Lines.Add(FGongFu);

end;

{ TFongFuNo }

procedure TFongFuNo.Operation;

begin

inherited;

FGongFu := '无功夫,需要学习';

WriteLog;

end;

end.

{调用}

unit Unit1;

interface

uses

Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

Dialogs, StdCtrls;

type

TForm1 = class(TForm)

Button1: TButton;

Memo1: TMemo;

procedure Button1Click(Sender: TObject);

private

procedure GongFun;

{ Private declarations }

public

{ Public declarations }

end;

var

Form1: TForm1;

implementation

uses Decorator;

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);

begin

GongFun;

end;

procedure TForm1.GongFun;

var

{猴子}

Monkey: TMonkey;

{无功夫}

FongFuNo: TFongFuNo;

{腾云驾雾}

GongFuKey: TGongFuKey;

{翻筋斗}

GongFuSomeRsault: TGongFuSomeRsault;

{变树、美女}

GongFuChange: TGongFuChange;

begin

{猴子}

Monkey := TMonkey.Create;

{无功夫}

FongFuNo := TFongFuNo.Create;

{腾云驾雾}

GongFuKey := TGongFuKey.Create;

{翻筋斗}

GongFuSomeRsault := TGongFuSomeRsault.Create;

{变树、美女}

GongFuChange := TGongFuChange.Create;

Memo1.Lines.Clear;

{注意装饰模式中，对象创建的先后顺序是可以随时可以变化的}

{情况之一 的猴子}

{

无功夫,需要学习

已经学会腾云驾雾之术

已经学会翻跟斗

已经变美女和变树

}

Form1.Memo1.Lines.Add('情况之一 的猴子: ');

FongFuNo.SetGongFuMonkey(Monkey);

GongFuKey.SetGongFuMonkey(FongFuNo);

GongFuSomeRsault.SetGongFuMonkey(GongFuKey);

GongFuChange.SetGongFuMonkey(GongFuSomeRsault);

GongFuChange.Operation;

Form1.Memo1.Lines.Add(' ');

Form1.Memo1.Lines.Add(' ');

{情况之二 的猴子}

{无功夫,需要学习

已经变美女和变树

已经学会腾云驾雾之术

已经学会翻跟斗}

Form1.Memo1.Lines.Add('情况之二 的猴子: ');

FongFuNo.SetGongFuMonkey(Monkey);

GongFuChange.SetGongFuMonkey(FongFuNo);

GongFuKey.SetGongFuMonkey(GongFuChange);

GongFuSomeRsault.SetGongFuMonkey(GongFuKey);

GongFuSomeRsault.Operation;

end;

end.

{Frm 文件}

object Form1: TForm1

Left = 297

Top = 186

Width = 312

Height = 392

Caption = 'Form1'

Color = clBtnFace

Font.Charset = DEFAULT_CHARSET

Font.Color = clWindowText

Font.Height = -11

Font.Name = 'MS Sans Serif'

Font.Style = []

OldCreateOrder = False

PixelsPerInch = 96

TextHeight = 13

object Button1: TButton

Left = 8

Top = 312

Width = 193

Height = 25

Caption = '测试-策略模式用例'

TabOrder = 0

OnClick = Button1Click

end

object Memo1: TMemo

Left = 8

Top = 8

Width = 249

Height = 297

Lines.Strings = (

'Memo1')

TabOrder = 1

end

end