[DUG] [computing] IsClass access violation

[Peter Ingham]

It will definitely occur if the instance is nil.


Cheers
On 14/11/2013 3:51 p.m., Ross Levis wrote:
>
> I've got a strange error occurring for just one user where this 
> procedure is failing...
>
> procedure TCustomDetails.SetModified(Modify: Boolean);
>
> begin
>
>   FModified := Modify;
>
>   if Modify then
>
>   begin
>
>     if Self is TCategoryDetails then MainForm.CategoryChanged := True
>
>     else MainForm.SpotChanged := True;
>
>   end;
>
> end;
>
> TCategoryDetails and another class is inherited from TCustomDetails.
>
> Access violation at address 004047DC in module 'SPLCreator.exe'. Read 
> of address FFFFFFDF.
>
> main thread ($87c):
>
> 004047dc SPLCreator.exe System                TObject.InheritsFrom
>
> 00404742 SPLCreator.exe System                @IsClass
>
> 005dc6a6 SPLCreator.exe SPMain      3831 +4 TCustomDetails.SetModified
>
> Would this happen if Self was nil or invalid?  I don't see how that 
> could happen but just wondering how this can happen.
>
> Cheers,
>
> Ross.
>
>
>
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