娃娃鸭Delphi面向对象编程思想刘艺笔记

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娃娃鸭Delphi面向对象编程思想刘艺笔记

2013年09月14日 ⁄ 综合 ⁄ 共 4401字 ⁄ 字号小中大 ⁄ 评论关闭

1、自动生命周期的整理

unit mtReaper;

interface

type

ImtReaper = interface

['{F3E97960-3F35-11D7-B847-001060806215}']

end;

TmtReaper = class(TInterfacedObject, ImtReaper)

private

FObject: TObject;

public

constructor Create(AObject: TObject);

destructor Destroy; override;

end;

implementation

uses SysUtils;

constructor TmtReaper.create(AObject: TObject);

begin

FObject := AObject;

end;

destructor TmtReaper.Destroy;

begin

FreeAndNil(FObject);

inherited;

end;

end.

=====================================================================

unit frmMain;

interface

uses

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

Dialogs, StdCtrls;

type

TNoisyDeath = class(TObject)

public

destructor Destroy; override;

end;

TForm1 = class(TForm)

Button1: TButton;

Button2: TButton;

procedure Button1Click(Sender: TObject);

procedure Button2Click(Sender: TObject);

private

procedure WaitAWhile;

public

{ Public declarations }

end;

var

Form1: TForm1;

implementation

uses mtReaper;

{$R *.dfm}

destructor TNoisyDeath.Destroy;

begin

showMessage('对象销毁了！');

inherited;

end;

procedure TForm1.WaitAWhile;

var

i: Integer;

begin

for i := 0 to 5000 do

begin

caption := Inttostr(i);

end;

procedure TForm1.Button1Click(Sender: TObject);

var

NoisyDeath: TNoisyDeath;

begin

NoisyDeath := TNoisyDeath.create;

try

waitAWhile;

finally

NoisyDeath.Free;

end;

procedure TForm1.Button2Click(Sender: TObject);

var

NoisyDeath: TNoisyDeath;

girm: ImtReaper;

begin

NoisyDeath := TNoisyDeath.create;

girm := TmtReaper.Create(NoisyDeath);

waitAWhile;

end;

end.

Decorator模式

·在不影响其他对象的情况下，以动态、透明度的方式给单个对象添加职责

·处理那些可以撤消的职责

·当不能采用生成子类的方法进行扩充时。一种情况是，可能有大量独立的扩展，为支持每一种组合将产生大量的子类，使得子类数目呈爆炸性增长；另一种情况可能是，因为类定义被隐藏，或类定义不能用于生成子类。

自动恢复字体

unit uSnapshot;

interface

uses SysUtils, mtReaper,classes;

type

ISnapshot=interface

['{FA256FA8-211F-462D-890B-FC0EB6096AD8}']

procedure Restore;

end;

TSnapshot=class(TInterfacedObject,ISnapshot)

private

FOriginal:TPersistent;

FTarget:TPersistent;

FReaper:ImtReaper;

public

constructor Create(Target:TPersistent);

destructor Destroy;override;

procedure Restore;

end;

implementation

constructor TSnapshot.create(Target:TPersistent);

begin

FOriginal:=TPersistent(Target.classType.create);

FReaper:=TmtReaper.create(FOriginal);

FTarget:=Target;

FOriginal.Assign(Target);

end;

destructor TSnapshot.Destroy;

begin

restore;

Inherited;

end;

procedure TSnapshot.Restore;

begin

if FTarget<>nil then

FTarget.Assign(FOriginal);

end;

end.

unit Unit1;

interface

uses

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

Dialogs, StdCtrls, ComCtrls;

type

TForm1 = class(TForm)

FontDialog1: TFontDialog;

btnSet: TButton;

Memo1: TMemo;

procedure btnSetClick(Sender: TObject);

procedure FormCreate(Sender: TObject);

procedure WaitAWhile;

private

public

{ Public declarations }

end;

var

Form1: TForm1;

implementation

uses uSnapshot;

{$R *.dfm}

procedure TForm1.btnSetClick(Sender: TObject);

var

FontSnapshot: ISnapshot;

begin

FontSnapshot := TSnapshot.Create(Memo1.Font);

{这里可以填写可能会改变TFont状态的任何代码}

if FontDialog1.Execute then

Memo1.Font := FontDialog1.Font;

Memo1.Update;

WaitAWhile;

end;

procedure TForm1.FormCreate(Sender: TObject);

begin

Memo1.Lines.Add(

'一个模拟对象状态改变后自动恢复的例子。');

end;

procedure TForm1.WaitAWhile;

var i: Integer;

begin

for i := 0 to 5000 do

begin

caption := '状态恢复倒计时:' + Inttostr(5000 - i);

end;

end.

这个例子确实有点份量，说明一些问题。

2、 TObject 类

1. inheritsFrom 判断一个类是否另一类的祖先类

2. 下面三种方案是分别运行的。

procedure TForm1.onclick(Sender: TObject);

var

str: string;

tmpclass: TObject;

classref: TClass;

begin

///第一种最简单的解决方案

str := '';

ListBox1.Items.Add(str);

str := format('Class Name = %s', [sender.ClassName]);

ListBox1.Items.Add(str);

str := format('Class Parent = %s', [sender.ClassParent.ClassName]);

ListBox1.Items.Add(str);

str := format('InstanceSize = %d', [sender.InstanceSize]);

ListBox1.Items.Add(str);

//以下为第二种，复杂的解决方案

tmpclass := sender;

while tmpClass.ClassParent <> nil do

begin

str := tmpclass.ClassName;

listbox1.Items.Add(str);

tmpclass := tmpclass.ClassParent.Create;

end;

{方案三}

listbox1.Items.Add('============================');

classref := sender.ClassType;

while classref <> nil do

begin

listbox1.Items.Add(classref.ClassName);

classref := classref.ClassParent;

end;

3、 TPersistent类

1.TPersistent类在Delphi类中的地位不亚于TObject类，该类定义于Classes单元中，Delphi中定义的类几乎都是由该类派生而来的。TPersistent之所以在Delphi类中居于如此重要的地位是因为它是Delphi可视化编程的基础。该类实现了对象公布(published)属性的存取，即在该类及其派生类中声明为published的属性、方法和事件等可在设计期时显示在Object Inspector窗体或数据模块的DFM 文件中。当Delphi 重新打开原来保存的窗口时，对象的设置值将被Delphi从DFM文件中读出。在程序运行期，对象将被初始化为设计期所设置的状态。