[rules-users] Re: About for and inheritance

[Edson Tirelli]

   Ideal IMO would be a compile time error, since getLikes() returns a
Cheese instance, but as we use MVEL to resolve the expression, I'm not 100%
sure we are able to cover all possible scenarios at compile time. I guess we
can, but need to double check that.

   []s
   Edson

2007/9/27, Chris Woodrow <woodrow.chris at gmail.com>:
>
> Thanks.
> I was supposing so...
> Do you think test 3 should throw a ClassCastException or just not match?
> Chris
>
> 2007/9/27, Edson Tirelli < tirelli at post.com >:
> >
> >
> >    Yes, drools is deferring the type verification until it is needed (in
> > your example, to check the constraint). May I ask you please to open a
> > JIRA... I will fix that.
> >
> >   []s
> >   Edson
> >
> > 2007/9/27, Chris Woodrow <woodrow.chris at gmail.com>:
> >
> > >  I am sorry I didn't mean 'for' but 'from'.
> > > :D
> > >
> > > 2007/9/27, Chris Woodrow < woodrow.chris at gmail.com>:
> > > >
> > > > Hi,
> > > > I recently find out a few issues using for, and I wanted to share it
> > > > with you. I made a simple exemple to illustrate my purpose.
> > > >
> > > > My classes are (I did not represent accessors & constructors):
> > > >
> > > > public class Cheese {
> > > >     protected String name;
> > > > }
> > > >
> > > > public class FrenchCheese extends Cheese{
> > > >     private String smell;
> > > > }
> > > >
> > > > public class Person {
> > > >     private Cheese likes;
> > > > }
> > > >
> > > > Here is my rule set :
> > > >
> > > > package rules
> > > >
> > > > rule "likes cheese"
> > > >     when
> > > >         $person : Person ()
> > > >         Cheese(  ) from $person.getLikes()
> > > >     then
> > > >         System.out.println ("likes cheese");
> > > > end
> > > >
> > > >
> > > > rule "likes french cheese"
> > > >     when
> > > >         $person : Person ()
> > > >         FrenchCheese(  ) from $person.getLikes()
> > > >     then
> > > >         System.out.println ("likes french cheese");
> > > > end
> > > >
> > > > First test :
> > > >         Cheese cheese = new FrenchCheese("good", "camembert");
> > > >         Person person = new Person();
> > > >         person.setLikes(cheese);
> > > >
> > > > Output :
> > > > likes french cheese
> > > > likes cheese
> > > >
> > > > Wich is expected...
> > > >
> > > > Second test :
> > > >         Cheese cheese = new Cheese();
> > > >         Person person = new Person();
> > > >         person.setLikes(cheese);
> > > >
> > > > Output :
> > > > likes french cheese
> > > > likes cheese
> > > >
> > > > That's the first strange thing. As far as I am concerned, rule
> > > > "likes french cheese" should not match (since a Cheese is not a
> > > > FrenchCheese).
> > > >
> > > > I made a change to the second rule :
> > > > rule "likes french cheese"
> > > >     when
> > > >         $person : Person ()
> > > >         FrenchCheese( smell == "good" ) from $person.getLikes()
> > > >     then
> > > >         System.out.println("likes french cheese");
> > > > end
> > > >
> > > > Third test :
> > > >         Cheese cheese = new Cheese();
> > > >         Person person = new Person();
> > > >         person.setLikes(cheese);
> > > >
> > > > output :
> > > > It throwed an exception : Exception in thread "main"
> > > > java.lang.ClassCastException: rules.Cheese
> > > > I am not saying the ClassCastException is not to expect in such a
> > > > case but I think I would simply expect it not to match (as far as a Cheese
> > > > is not a FrenchCheese).
> > > >
> > > > Chris
> > > >
> > >
> > >
> > > _______________________________________________
> > > rules-users mailing list
> > > rules-users at lists.jboss.org
> > > https://lists.jboss.org/mailman/listinfo/rules-users
> > >
> > >
> >
> >
> > --
> >   Edson Tirelli
> >   Software Engineer - JBoss Rules Core Developer
> >   Office: +55 11 3529-6000
> >   Mobile: +55 11 9287-5646
> >   JBoss, a division of Red Hat @ www.jboss.com
> > _______________________________________________
> > rules-users mailing list
> > rules-users at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
>
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>


-- 
  Edson Tirelli
  Software Engineer - JBoss Rules Core Developer
  Office: +55 11 3529-6000
  Mobile: +55 11 9287-5646
  JBoss, a division of Red Hat @ www.jboss.com
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