if not Assigned(Modeless) then Assigned()什么意思! assigned 是用来判断某一指针(pointer)或过程引用是否为nil(空),如果为空则返回假(false). 用法示例(防止窗体被实例化多次): unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls; type…