关于类的入门的例子(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.