unit Unit1;interfaceuses  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, StdCtrls, ExtCtrls;type  TForm1 = class(TForm)    RadioGroup1: TRadioGroup;    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;      Shift: TShiftState; X, Y: Integer);    procedure FormCreate(Sender: TObject);    procedure RadioGroup1Click(Sender: TObject);  private    { Private declarations }  public    { Public declarations }  end;var  Form1: TForm1;implementation{$R *.dfm}var  ClassRef: TControlClass;  //TControlClass 是 TControl 的类引用procedure TForm1.FormCreate(Sender: TObject);begin  RadioGroup1.Width := 300;  RadioGroup1.Columns := 3;  RadioGroup1.Items.Add('Button');  RadioGroup1.Items.Add('Edit');  RadioGroup1.Items.Add('Lable');  RadioGroup1.ItemIndex := 0;  ClassRef := TButton;end;procedure TForm1.RadioGroup1Click(Sender: TObject);begin  case RadioGroup1.ItemIndex of    0: ClassRef := TButton;    1: ClassRef := TEdit;    2: ClassRef := TLabel;  end;end;procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;  Shift: TShiftState; X, Y: Integer);var  NewCtrl: TControl;begin  NewCtrl := ClassRef.Create(Self);  NewCtrl.Name := ClassRef.ClassName + IntToStr(Self.ControlCount);  NewCtrl.Parent := Self;  NewCtrl.Left := X;  NewCtrl.Top := Y;end;end.