[rules-users] About for and inheritance

[Wolfgang Laun]

On 15 January 2011 11:32, Evert Penninckx <evert.penninckx at gmail.com> wrote:

>
> I thought I had an error from the drools plugin when using instanceof even
> in eval, but I'll try that again, I think I tried eval(this instanceof
> ...).
>

You cannot use this in an eval. The eval is "moved out" from the containing
pattern,
and there this has no meaning.


>
> Overloading getLikes() would be more elegant. Still, for me these are
> workarounds.
>
> Would it be that strange or unconventional to have the from only match on
> the required subclass?
>

Given that getLikes() is *your *choice of method producing the data, and
that
FrenchCheese is *your *choice of type for the receiver: would it be that
strange
or unconventional to expect you to employ matching types? ;-)

Type checking should not result in the silent elimination of data at
runtime. What
I would expect Drools to tell me is the incompatibility of the from and the
receiving
pattern, at compile time.

-W




>
> Grtz
>
> Evert
>
>
> Wolfgang Laun-2 wrote:
> >
> > If smell is a property of Cheese and not just of FrenchCheese you could
> > use
> >
> >
> > when
> >        $person : Person ()
> >        $c: Cheese( eval( $c instanceof FrenchCheese), smell == "good" )
> > from
> > $person.getLikes()
> > then
> >
> > Also, I think that a selective retrieval with an overloaded version of
> > getLikes():
> >    getLikes( Class clazz )
> > might be useful, avoiding useless elements in the returned collection.
> >
> > -W
> >
> >
> --
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> http://drools-java-rules-engine.46999.n3.nabble.com/About-for-and-inheritance-tp54110p2260831.html
> Sent from the Drools - User mailing list archive at Nabble.com.
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