Пример класса

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
type
  Tblabla = class(TObject)
    Surname: String;
    Year: Integer;
    function haha(i: integer): string;
  end;
var
  Form1: TForm1;

implementation

{$R *.dfm}



function Tblabla.haha(i: integer): string;
begin
result:=IntToStr(i);
end;

procedure TForm1.Button1Click(Sender: TObject);
var   blabla1: Tblabla;
begin
blabla1:=Tblabla.Create;
blabla1.Year:=40;
blabla1.Surname:=blabla1.haha(blabla1.Year);
showmessage(blabla1.Surname);
FreeAndNil(blabla1);
end;
end.