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
On 14 January 2011 12:02, Evert Penninckx <[email protected]> wrote:
>
> Hi
>
> I stumbled upon this problem last week. I see this is a very old post, and
> I
> was wondering if a "solution" has been implemented?
>
> It seems logical to me, that "from" only matches if an element in the list
> matches the required subclass. This means the classcast exception is
> catched
> and causes the rule not to match.
> rule "likes french cheese"
> when
> $person : Person ()
> FrenchCheese( smell == "good" ) from $person.getLikes()
> then
> System.out.println("likes french cheese");
> end
> This rule should only match FrenchCheese, even if other subclasses of
> Cheese
> are present in the set of Cheeses (getLikes()).
>
>
> They way I avoid it now is using an Enum containing each Cheese class
> (since
> I can't get it working with reflection).
> rule "likes french cheese"
> when
> $person : Person ()
> $cheese : Cheese( cheeseType == CheeseTypes.FrenchCheese ) from
> $person.getLikes()
> FrenchCheese( smell == "good" ) from $cheese
> then
> System.out.println("likes french cheese");
> end
> A bit awkward in my opinion. It would be nice if drools provided for the
> matching itself.
>
>
> So again, has this "problem" evolved since 2007?
>
>
>
> Greetz
>
> Evert
>
>
>
> --
> View this message in context:
> http://drools-java-rules-engine.46999.n3.nabble.com/About-for-and-inheritance-tp54110p2254750.html
> Sent from the Drools - User mailing list archive at Nabble.com.
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> rules-users mailing list
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>
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