unit Unit1;

{$mode objfpc}{$H+}

interface

uses
  Classes, StdCtrls, SysUtils, Forms, Controls, Graphics, Dialogs;

type

  { TForm1 }

  TForm1 = class(TForm)
    ComboBox1: TComboBox;
    Label1: TLabel;
    procedure ComboBox1Change(Sender: TObject);
    procedure FormClose(Sender: TObject; var CloseAction: TCloseAction);
    procedure FormCreate(Sender: TObject);
  private
    FStrList: TStringList;
    procedure SetStrList(AValue: TStringList);

  public
    property StrList: TStringList read FStrList write SetStrList;
  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}

{ TForm1 }

procedure TForm1.FormCreate(Sender: TObject);
var
  i: PtrInt = 0;
begin
  FStrList:= TStringList.Create;

  for i:= 0 to 9 do
    StrList.AddObject(Format('string_%d (added as Object: %d)',[Succ(i),i]),TObject(i));

  ComboBox1.Items.Assign(StrList);
  ComboBox1.ItemIndex:= 0;
  ComboBox1Change(Sender);
end;

procedure TForm1.FormClose(Sender: TObject; var CloseAction: TCloseAction);
begin
  FreeAndNil(FStrList);
end;

procedure TForm1.ComboBox1Change(Sender: TObject);
begin
  Label1.Caption:= 'PtrInt(Object): ' + IntToStr(PtrInt(ComboBox1.Items.Objects[ComboBox1.ItemIndex]));
end;

procedure TForm1.SetStrList(AValue: TStringList);
begin
  if StrList.Equals(AValue) then Exit;
  FStrList.Assign(AValue);
end;

end.