[fpc-pascal] casting interfaces and objects

Marc Santhoff M.Santhoff at t-online.de
Mon May 19 00:02:55 CEST 2008

Am Sonntag, den 18.05.2008, 23:41 +0200 schrieb Graeme Geldenhuys:
> 2008/5/18 Marc Santhoff <M.Santhoff at t-online.de>:
> > Since the compiler dod not warn about using the "as" operator I assume
> > it is safe? Like this:
> >
> > procedure TObservable.DeRegister( obsv: IObserver );
> > var
> >        i: integer;
> > begin
> >        if (fObservers.count<=0) then exit;
> >        for i:=0 to fObservers.count-1 do begin
> >                if ((fObservers[i] as IObserver)=obsv) then begin
> I'm not a big Interfaces expert, but as for as I know using 'as' like
> that with Interfaces actually translates to a QueryInterface() call
> internally, which is why it is allowed.  I vaguely remember as issue
> between CORBA and COM interfaces and the 'as' call, because CORBA
> interfaces do not have a QueryInterface() implementation. Well,
> something like that... :-)

Okay, so there are still some unknowns.

However, before something goes into production I'll put up some tests
for the cases in question.

Thanks again, to Marco too,

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