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µ±Ä㽨¹¹Ò»¸öÎï¼þ SomeComponet.Create(Owner);
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µ±Äã½â¹¹Ò»¸öÎï¼þ SomeComponet.Free;
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If Assigned(SomeComponet) then SomeComponet := nil;
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function Assigned(var 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.
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if assigned(frm) then frm.close; µ«Êǵ±Ï´ε÷ÓÃʱ¾Í»á³ö´í¡£ÎªÊ²Ã´ÄØ£¬Ö±µ½Õ¦ÌìÎÒ²ÅÖªµÀÔÒò
frm.close;frm.free; Ö»ÊÇÖ¸¶¨Õâ¿éÄÚ´æ¿ÉÒÔÖØÐ´£¬²¢Î´ÊÍ·ÅΪNIL Òò´Ëµ±Ï´ε÷ÓÃʱ¼´Ê¹frm.freeÒѾ
Ö´Ðйýassigned(frm)ÈÔΪTRUE£¬ÔÙ´ÎÊÍ·Å frm.Close »òÕß frm.free ¿Ï¶¨»á±¨´í£»Ó¦Îªfrm.Close»òfrm.free ÊÇÊÍ·Å ¶ÔÏóÖ¸Õëfrm Ö¸ÏòµÄÄÚ´æ¿Õ¼ä£¬ÔÚÉÏ´ÎÒѾÊͷŵ÷ÁË£¬µ«ÊÇ frm ±¾Éí²¢Ã»ÓÐ ³õʼ»¯Îª nil ,Ïà·´Ëü»¹ÊÇÖ¸Ïò±»ÊͷŵÄÄÚ´æµØÖ·£»¶«Î÷ÒѾûÓÐÁË£¬Ã»Óеض«Î÷È¥ÊÍ·Å£¬²»±¨´í´í²Å¹Ö¡£
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if assigned(frm) then
begin
frm.close;
frm:=nil;
end;
»ò:
if assigned(frm) then
begin
frm
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unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,Dialogs;
type
TForm1 = class(TForm)
procedure one();
function two(x,y:integer):integer;
private
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