写成函数，就找不到控件了

unit GG;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, IdBaseComponent, IdComponent, IdTCPConnection, IdTCPClient,
IdHTTP, ExtCtrls, StdCtrls;

type
TForm1 = class(TForm)
Edit1: TEdit;
Edit2: TEdit;
Timer1: TTimer;
IdHTTP1: TIdHTTP;
procedure Timer1Timer(Sender: TObject);

private
{ Private declarations }

public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}
function zhonghang():string;
begin

with TStringList.Create do try
Text := IdHTTP1.Get('http://www.xxx.com');
if Count > 2 then
begin
edit1.Text:= Copy(Strings[Count - 2], 0, 8);
edit2.Text:= Copy(Strings[Count - 2], 0, 8);
end;
finally
Free;
end;
end;

procedure TForm1.Timer1Timer(Sender: TObject);
begin
zhonghang();
end;

end.
错误：
[Error] GGold.pas(47): Undeclared identifier: 'IdHTTP1'
[Error] GGold.pas(50): Undeclared identifier: 'edit1'
[Error] GGold.pas(51): Undeclared identifier: 'edit2'

这段不对了？？
找不到控件，
函数放错位置了？