[rules-users] How to limit results from a collect statement

[Edson Tirelli]

   If you want the "engine to see" your changes, in a way you affect other
rules, you must call update( object ) for the object you are changing.
Otherwise, the change will happen to the original object, but not to the
shadow proxy that the engine uses to ensure consistency.

   []s
   Edson

2007/8/22, pentarious <cristiano.giuffrida at gmail.com>:
>
>
> Ok, I'm still working on that, I'll publish my solution asap. In the
> meantime
> it turns out our requirements need something more than that. We have an
> ordered list of beans (items) and we have to be able to modify a specific
> subset of the list (adding a discount). Now I tried to solve this problem
> by
> working directly on the list of items. But I can't understand why this
> doesn't work:
> when
>      $itemList : ArrayList() from collect( Item( category == "VIDEO" ) )
> then
>      ItemDiscount disc = new ItemDiscount(10);
>      $myFirstItem = (Item)$itemList.get(0);
>      $mySecondItem = (Item)$itemList.get(1);
>      $myFirstItem.addDiscount(disc);
>      $mySecondItem.addDiscount(disc);
>
> After executing this rule it's like nothing happened! I mean no discount
> has
> been added to the two items! The problem seems to be related to extracting
> items from the list. Apparently, every time we get an item from the list,
> it
> looses its link with the original item (I don't know if it's a copy of the
> original item or whatever), so that every update doesn't affect the
> original
> item any more. But of course that's what we're interested in! We want to
> modify original items in the rule session. Am I missing something? Or Is
> it
> a bug?
>
> Regards,
>
> CG
>
>
>
> Edson Tirelli-3 wrote:
> >
> >     Please, share with us! Send to the list!
> >
> >     Edson
> >
> > 2007/8/21, pentarious <cristiano.giuffrida at gmail.com>:
> >>
> >>
> >> I found an interesting implementation to do that. If anyone is
> interested
> >> I
> >> could share my solution.
> >>
> >> Regards,
> >>
> >> CG
> >>
> >>
> >> Mark Proctor wrote:
> >> >
> >> > There is no supported way to do this. You could use an inline-eval
> >> > against a global, but that is very clunkey. However it does seem like
> a
> >> > good feature idea for a future release, open a jira and I'll look
> into
> >> > getting it included.
> >> >
> >> > Mark
> >> > pentarious wrote:
> >> >> Does anyone know a method to limit the number of results from a
> >> collect
> >> >> statement? I was just wondering how to do something like this:
> >> >> $myList : List() from collect( MyObject(myField == "something") )
> >> limit
> >> 3
> >> >> //it should put in $myList just the first 3 objects retrieved
> >> >> I'm quite sure there is nothing in Drools which can natively support
> >> >> something like that. So, how to do that, if needed? I tried this,
> but
> >> it
> >> >> seems not to be working (I can't understand why, though):
> >> >> $myList : List() from collect( MyObject(myField == "something") )
> >> >> $myObject : MyObject() from $myList
> >> >> eval( $myList.indexOf($myObject) < 3 )
> >> >> Indeed, it doesn't work because the link beetween $myList and
> >> $myObject
> >> >> seems to be released during any execution of the rule (In fact
> >> >> $myList.contains($myObject) returns false! Again, I can't understand
> >> >> why...)
> >> >>
> >> >> Any advice would be really appreciated!
> >> >>
> >> >> Regards,
> >> >>
> >> >> CG
> >> >>
> >> >
> >> > _______________________________________________
> >> > rules-users mailing list
> >> > rules-users at lists.jboss.org
> >> > https://lists.jboss.org/mailman/listinfo/rules-users
> >> >
> >> >
> >>
> >> --
> >> View this message in context:
> >>
> http://www.nabble.com/How-to-limit-results-from-a-collect-statement-tf4235669.html#a12249025
> >> Sent from the drools - user mailing list archive at Nabble.com.
> >>
> >> _______________________________________________
> >> 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
> >
> >
>
> --
> View this message in context:
> http://www.nabble.com/How-to-limit-results-from-a-collect-statement-tf4235669.html#a12270505
> Sent from the drools - user mailing list archive at Nabble.com.
>
> _______________________________________________
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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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