P,
Thanks for that. Makes sense.... It really had me perplexed. I guess as a
rule of thumb an Application.ProcessMessafes should be placed after Close
calls where the OnClose sets Action := caFree;
------------------------------------------------------------------------
--Donovan
Donovan J. Edye [www.edye.wattle.id.au]
Namadgi Systems, Delphi Developer
Web: www.namsys.com.au E-Mail: [EMAIL PROTECTED]
Voice: +61 2 6285-3460 Fax: +61 2 6285-3459
TVisualBasic = Class(None);
------------------------------------------------------------------------
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On
> Behalf Of Paul Heinz
> Sent: Wednesday, 10 November 1999 10:01
> To: Multiple recipients of list delphi
> Subject: RE: [DUG]: Freeing forms..... Confusion....
>
>
> Donovan wrote:
> > Given TForm1, TForm2 (TForm1 is the main form and TForm2 is NOT
> > automatically created) with the following code:
> >
> > Instance1:
> >
> > No code in form2 and the following works as expected. Form2 is shown,
> > closed.
> >
> > procedure TForm1.Button1Click(Sender: TObject);
> > begin
> > try
> > Application.CreateForm(TForm2, Form2);
> > Form2.Show;
> > Sleep(2000);
> > Form2.Close;
> > Sleep(2000);
> > //ShowMessage('Hello');
> > Form2.Caption := 'I was never freed';
> > Form2.Show;
> > except
> > on E : Exception do
> > ShowMessage(E.Message);
> > end;
> > end;
> >
> > Instance2:
> >
> > procedure TForm2.FormClose(Sender: TObject; var Action: TCloseAction);
> > begin
> > Action := caFree;
> > end;
> >
> > TForm1 code from above. Why do I not get an access violation when
> > I attempt
> > to set the caption? The close event has triggered and the action
> > should have
> > freed the form. Put a showmessage PRIOR to the caption being set
> > and you get
> > an access violation. Can someone explain this to me?
>
> Using caFree causes Form.Release to be called during Close. Now
> Form.Release
> does not immediately call Destroy, rather it posts a message into the
> windows message queue to call Form.Destroy later.
>
> This is done so that Release can be called inside a method of the
> Form to be
> destroyed. So, until you actually enter a message loop or call
> Application.ProcessMessages, Form2 still exists.
>
> Now, guess what ShowMessage does? Yes, it enters a message loop so Form2
> _will_ be destroyed by the time you set Form2.Caption.
>
> TTFN,
> Paul.
>
>
> ------------------------------------------------------------------
> ---------
> New Zealand Delphi Users group - Delphi List - [EMAIL PROTECTED]
> Website: http://www.delphi.org.nz
>
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