unit Unit2;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Controls,
  Dialogs, ExtCtrls, ShellAPI, AppEvnts, Forms;
type
  IFruitInterface = interface
    ['{D4557157-5241-4116-AA1E-87F86A884EA9}']
    procedure grow();
    procedure harvest();
    procedure plant();
  end;

type
  TApple = class(TComponent, IFruitInterface)
  private
    treeAge: Integer;
  public
    procedure grow();
    procedure harvest();
    procedure plant();
  end;

  TStrwaBerry = class(TComponent, IFruitInterface)
  private
    treeAge: Integer;
  public
    procedure grow();
    procedure harvest();
    procedure plant();
  end;
  TGrape = class(TComponent, IFruitInterface)
  private
    treeAge: Integer;
  public
    procedure grow();
    procedure harvest();
    procedure plant();
  end;

  TFruitGarden = class
  public
    class function GetFruit(const strFruit: string): IFruitInterface;
  end;

implementation
//{$R *.dfm}
procedure TApple.grow();
begin
  showmessage('Apple grow');
end;

procedure TApple.harvest();
begin
  showmessage('Apple harvest');
end;

procedure TApple.plant();
begin
  showmessage('Apple plant');
end;

procedure TStrwaBerry.grow();
begin
  showmessage('StrwaBerry plant');
end;

procedure TStrwaBerry.harvest();
begin
  showmessage('StrwaBerry plant');
end;

procedure TStrwaBerry.plant();
begin
  showmessage('StrwaBerry plant');
end;

procedure TGrape.grow();
begin
  showmessage('Grape plant');
end;

procedure TGrape.harvest();
begin
  showmessage('Grape plant');
end;

procedure TGrape.plant();
begin
  showmessage('Grape plant');
end;

class function TFruitGarden.GetFruit(const strFruit: string): IFruitInterface;
begin
  if strFruit = 'Apple' then
    Result := TApple.create(nil)
  else if strFruit = 'StrawBerry' then
    Result := TStrwaBerry.create(nil)
  else if strFruit = 'Grape' then
    Result := TGrape.create(nil)
  else
    raise Exception.Create('Cannot create ' + strFruit);
end;

end.

//test

  AFruitGarden: TFruitGarden;
  AFruit: IFruitInterface;
begin

  AFruitGarden := TFruitGarden.Create();
  try
    AFruit := AFruitGarden.GetFruit(Edit1.Text);
    AFruit.grow();
  except on FruitError: Exception do
      ShowMessage(FruitError.Message);
  end;

  FreeAndNil(AFruitGarden);
end;