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How to destroy all the labels on a panel, leaving other controls untouched?

Posted on 2004-09-01
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Last Modified: 2010-04-05
Hi

I have written the following code to destroy only the labels on a panel in a form's Close event.
But when I run it, I get the error:
" Project . . . raised exception class EListError with message 'List index out of bounds(1)'. " 
This seems to occur when the control encountered is not a label.

Am I doing something stupid? Or if this method is not allowed, how do I do what I want to do?

procedure PanLabsDestroy(p:tpanel);
{   This destoys all labels on panel p  }
var
  i:integer;
  lab:tcontrol;
begin
  for i:=0 to p.controlcount-1 do
  begin
    lab:=p.controls[i];
    if lab is tlabel then lab.Destroy;
  end;
end;

Help appreciated!

tiggermark
0
Comment
Question by:tiggermark
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5 Comments
 
LVL 13

Accepted Solution

by:
BlackTigerX earned 50 total points
ID: 11955771
try doing it in reverse order

for i:=p.ControlCount-1 downto 0 do
0
 

Author Comment

by:tiggermark
ID: 11955910
Thanks very much. That works.

Can't think why the other doesn't though. It's all a plot!

tiggermark
0
 
LVL 13

Expert Comment

by:BlackTigerX
ID: 11956305
because you are deleting, so the count decreases... makes sense?

after you delete one, p.ControlCount is messed up, but the original count was for example 5, and now is 4, therefor 5 doesn't exist anymore, and you get an access violation

if you go in reverse order it doesn't matter if the count changes, because you are going towards zero, not towards the original count
0
 

Author Comment

by:tiggermark
ID: 11958157
Yes, I see.

An error occurs because one tries to use a no-longer-existing control.

Thanks.

The points are all yours!
0
 
LVL 13

Expert Comment

by:BlackTigerX
ID: 11958961
yes... that's what access violations are all about... trying to access something that doesn't exist
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