delphi中 怎么在一个库单元文件中调用另一个库单元文件的form（form要显示出来）
Unit1中：
unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, Buttons, ExtCtrls;

type
TForm1 = class(TForm)

procedure Button7Click(Sender: TObject);

implementation

uses Unit2 ;

procedure TForm1.Button7Click(Sender: TObject);
begin
TForm2.show;
end;

end.

Unit2中：
unit Unit2;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs ,Unit1 ;

type
TForm2 = class(TForm)
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form2: TForm2;

implementation

{$R *.dfm}

end.

编译时总是报错误：
Could not compile used unit 'Unit1.pas', 不知道是什么问题，请知道的童鞋帮帮忙 谢谢




[解决办法]
Unit1中：
procedure TForm1.Button7Click(Sender: TObject);
begin
Form2.show;
end;

TForm2是类，Form2才是对象