怎样判断窗体是否已经创建

[ss__328]

如题

[rtewryery]

if assign(form1)<>nil then
begin
dosomething;
end;

[blazingfire]

if Form1=nil then
//没有创建

[rtewryery]

if assinged(form1) then
begin
showmessage("窗体已经建立")；
end;

[cbdiy]

var kk:hwnd;
begin
kk:=findwindow(nil,'Form2');
if kk<>0 THEN showmessage('已存在');

[ihihonline]

if assinged(form1)
form1 := Tform1.Create(nil)

[fwwxxjingling]

the use of assigned:
****************************************************************
Tests for a nil (unassigned) pointer or procedural variable.

Unit

System

Category

miscellaneous routines

function Assigned(const P): Boolean;

Description

Use Assigned to determine whether the pointer or procedure referenced by P is nil. P must be a variable reference of a pointer or procedural type. Assigned(P) corresponds to the test P<> nil for a pointer variable, and @P <> nil for a procedural variable.

Assigned returns False if P is nil, True otherwise.

Note: Assigned can't detect a dangling pointer--that is, one that isn't nil but no longer points to valid data. For example, in the code example for Assigned, Assigned won't detect the fact that P isn't valid.
********************************************************************

[fwwxxjingling]

我一般是这样做的：
*************************************************************
if form1<>nil then
begin
form1=nil;
form1.free;
end;
form1:=Tform1.Create;
*************************************************************

[del_c_sharp]

呵呵,楼上是不是写反了
nil了以后,还free谁呢?

[zhxfzhxf1]

if Form1=nil then
。。。
else
。。。

[jeking]

用assinged(form1) 判断

[dupenf]

assign too