Delphi类的入门的例子(6): 类引用示例

unit Unit1;
interface
uses
　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.