工廠模式，有工廠就有產品，工廠里就是加工產品的，這個模式有以下參與者：

1.抽象產品，對象產品的對像接口或抽象層。

2.具體產口，實現抽象產品的接口。

3.抽象工廠，工廠的方法，方法用于反回產品對象。可以用抽象類或接口定義

4.具體工廠，實現抽象工廠接口的具體類

unit Unit4;

interface

uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs,
Vcl.StdCtrls;

type
TProcedure = class(TObject)//產品抽象類
public
procedure ShowCarName; virtual; abstract;
end;

TProcedureNissan = class(TProcedure) //產品具體類
public
procedure ShowCarName; override;
end;

TProcedureToyota = class(TProcedure) //產品具體類
public
procedure ShowCarName; override;
end;

TFactoryInterface = class(TObject) //工廠抽象類
public
function CreateProcedure: TProcedure; virtual; abstract;//返回產品
end;

TFactoryNissan = class(TFactoryInterface) //工廠具體類
public
function CreateProcedure: TProcedure; override;
end;

TFactoryToyota = class(TFactoryInterface) //工廠具體類
public
function CreateProcedure: TProcedure; override;
end;

TForm4 = class(TForm)
btn1: TButton;
btn2: TButton;
procedure FormCreate(Sender: TObject);
procedure btn1Click(Sender: TObject);
procedure btn2Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form4: TForm4;

implementation

{$R *.dfm}

procedure TForm4.btn1Click(Sender: TObject);
var
_CarFactory: TFactoryInterface;
_CarClass: TProcedure;
begin
_CarFactory := TFactoryNissan.Create;
_CarClass := _CarFactory.CreateProcedure;
_CarClass.ShowCarName;
_CarClass.Free;
_CarFactory.Free;
end;

procedure TForm4.btn2Click(Sender: TObject);
var
_CarFactory: TFactoryInterface;
_CarClass: TProcedure;
begin
_CarFactory := TFactoryToyota.Create;
_CarClass := _CarFactory.CreateProcedure;
_CarClass.ShowCarName;
_CarClass.Free;
_CarFactory.Free;
end;

procedure TForm4.FormCreate(Sender: TObject);
begin

end;

{ TProcedureToyota }

procedure TProcedureToyota.ShowCarName;
begin
ShowMessage('這個是豐田汽車 TOYOTA');
end;

{ TProcedureNissan }

procedure TProcedureNissan.ShowCarName;
begin
ShowMessage('這個是日產汽車 NISSAN');
end;

{ TFactoryNissan }

function TFactoryNissan.CreateProcedure: TProcedure;
begin
Result := TProcedure(TProcedureNissan.Create);
end;

{ TFactoryToyota }

function TFactoryToyota.CreateProcedure: TProcedure;
begin
Result := TProcedure(TProcedureToyota.Create);
end;

end.

總結，工廠模式一般用途返回一個對象，將產品和工廠進行分離后，各自進行抽象和多態。這個原型結構看似簡單但在實際使用過程中卻可以靈活運用。通過類中的工廠方法創建產品，可以系統在不修改具體的工廠角色的情況下引進新產品（擴展）。工

廠模式相當于給工廠派生一個掛鉤以便提供對象的一個擴充版本。