is 与 as 运算符举例

unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, ActnList, StdCtrls, ExtCtrls;



type

  TForm1 = class(TForm)

    Button1: TButton;

    Edit1: TEdit;

    procedure FormCreate(Sender: TObject);

  private

    procedure MyPro(Sender: TObject);

    { Private declarations }

  public

    { Public declarations }

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



procedure TForm1.FormCreate(Sender: TObject);

begin

  Button1.OnClick := MyPro;

  Edit1.OnClick := MyPro;

end;



procedure TForm1.MyPro(Sender: TObject);

begin

  if Sender is TButton then

    ShowMessage((Sender as TButton).Caption);



  if Sender.InheritsFrom(TEdit) then

    ShowMessage((Sender as TEdit).Text);

end;



end.