[rules-users] Re: About for and inheritance

[Edson Tirelli]

   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
> >
>
>
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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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