unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    RadioGroup1: TRadioGroup;
    btnCreate: TButton;
    GroupBox1: TGroupBox;
    procedure FormCreate(Sender: TObject);
    procedure RadioGroup1Click(Sender: TObject);
    procedure btnCreateClick(Sender: TObject);
    procedure ControlClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    x, y : integer;            //For positioning the controls
  end;

var
  Form1: TForm1;
  aControl : TControl;
  TheClass : TControlClass;    //The Class reference

implementation

{$R *.DFM}

procedure TForm1.FormCreate(Sender: TObject);
begin
  x := 184;
  y := 16;
  RadioGroup1.ItemIndex := 0;
end;

//Set the class references
procedure TForm1.RadioGroup1Click(Sender: TObject);
begin
  Case RadioGroup1.ItemIndex of
    0 : TheClass := TButton;
    1 : TheClass := TRadioButton;
    2 : TheClass := TCheckbox;
    3 : TheClass := TEdit;
  end;
end;

// create the control using the current classref
// and give it a name, notice that the name is automatic the caption
procedure TForm1.btnCreateClick(Sender: TObject);

begin
  x := x + 2;                        //Position the new control
  y := y + 25;
  aControl := TheClass.Create(Self);
  aControl.Parent := GroupBox1;
  aControl.Left := x;
  aControl.Top := y;
  aControl.Name := aControl.ClassName + IntToStr(x)+IntToStr(y);
  // Give the Buttons a OnClick event
  if aControl is TButton then
    (aControl as TButton).OnClick := ControlClick;  //Assign an onclick event
end;

// The Control onClick event for buttons
procedure TForm1.ControlClick(Sender: TObject);
begin
  aControl := Sender as TButton; // Set aControl object to the current clicked button
  ShowMessage('Clicked a control of class ' + aControl.name);
end;

end.