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Creating a form - a function controls it!

Posted on 2000-05-02
10
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Last Modified: 2010-04-04
I want to do a function. I'll control my form creation (my application will show only one form, non-modal)...

Here is the code:

function abreform(instancia: tcomponentClass; var Reference): boolean;
begin
   abreform := false;
   if not Assigned(tform(reference)) then
      begin
      application.CreateForm(instancia, Reference);
      abreform := true;
      end  
   else
      messagedlg('The form is opened', mtinformation, [mbok], 0);
end;

The problem is after the first form creation... The function don't restart the variable and returns 'Form is opened'... I've closed the respective form, and I did the caFree command...

Can you help me?!?

Thanks a lot!

Best regards,

Ricardo Baitz
0
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Question by:baitz
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10 Comments
 
LVL 10

Expert Comment

by:Lischke
ID: 2769484
Hi Ricardo,

this is the typical case where newbies have their problems with. Delphi does not automatically reset a reference variable to nil when the reference it points to is destroyed.

There's no harm (usually) when you set a forms reference variable to nil in the forms OnClose event. With Delphi 5 there's function FreeAndNil but you must not use this function within an event of the particular class as it frees the class for you are still executing code. But you can save assing nil to the reference variable.

Ciao, Mike
0
 
LVL 10

Expert Comment

by:ECollin
ID: 2769491
did you set your from to "nil" ?
0
 
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Expert Comment

by:ECollin
ID: 2769493
did you set your form to "nil" after the caFree ?
0
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Author Comment

by:baitz
ID: 2769525
Thks a lot! The problem was a nill after cafree...
0
 

Author Comment

by:baitz
ID: 2769526
This question has a deletion request Pending
0
 
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Expert Comment

by:Lischke
ID: 2769658
This question no longer is pending deletion
0
 
LVL 10

Accepted Solution

by:
Lischke earned 50 total points
ID: 2769660
Fine that I solved your problem. You should now accept one of my comments as answer and not just delete the question. This is not fair!

To make your decision easier I post an answer so you just need to accept.

Ciao, Mike
0
 

Author Comment

by:baitz
ID: 2812207
Thank you, mike... Your answer are correct... I don't read it in my book!

You was a lot of fast!
0
 

Author Comment

by:baitz
ID: 2812214
And more: Only today I've entered here to transfer the points... Too late, but transfered!
0
 
LVL 10

Expert Comment

by:Lischke
ID: 2813459
Okey, dokey :-)
0

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