Template 模式之Delphi实现

unit Tpl_meth;

{
Design pattern example -
some simple classes using the Template Method pattern.
}
interface

type
TAbstractTemplateClass = class(TObject)
protected
function Algorithm_StepA: Integer; virtual; abstract;
function Algorithm_StepB: Integer; virtual; abstract;
function Algorithm_StepC: Integer; virtual; abstract;
public
function Algorithm: Integer;
end;

TConcreteClassA = class(TAbstractTemplateClass)
protected
function Algorithm_StepA: Integer; override;
function Algorithm_StepB: Integer; override;
function Algorithm_StepC: Integer; override;
end;

TConcreteClassB = class(TAbstractTemplateClass)
protected
function Algorithm_StepA: Integer; override;
function Algorithm_StepB: Integer; override;
function Algorithm_StepC: Integer; override;
end;

implementation

function TAbstractTemplateClass.Algorithm: Integer;
begin
Result := Algorithm_StepA
Algorithm_StepB
Algorithm_StepC;
end;

function TConcreteClassA.Algorithm_StepA: Integer;
begin
Result := 1;
end;

function TConcreteClassA.Algorithm_StepB: Integer;
begin
Result := 2;
end;

function TConcreteClassA.Algorithm_StepC: Integer;
begin
Result := 3;
end;

function TConcreteClassB.Algorithm_StepA: Integer;
begin
Result := 4;
end;

function TConcreteClassB.Algorithm_StepB: Integer;
begin
Result := 5;
end;

function TConcreteClassB.Algorithm_StepC: Integer;
begin
Result := 6;
end;

end.

/////////////////////////////////////////////////////////////////////////////////

unit Unit1;

interface

uses
SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
Forms, Dialogs, StdCtrls;

type
TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.DFM}

uses tpl_meth;

procedure TForm1.Button1Click(Sender: TObject);
var
AnAbstractObject: TAbstractTemplateClass;
begin
AnAbstractObject := TConcreteClassA.Create;
try
ShowMessage(''''Algorithm Result = '''' Inttostr(AnAbstractObject.Algorithm));
finally
AnAbstractObject.Destroy;
end;
end;

procedure TForm1.Button2Click(Sender: TObject);
var
AnAbstractObject: TAbstractTemplateClass;
begin
AnAbstractObject := TConcreteClassB.Create;
try
ShowMessage(''''Algorithm Result = '''' Inttostr(AnAbstractObject.Algorithm));
finally
AnAbstractObject.Destroy;
end;
end;

end.

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