[rules-users] objects

[Edson Tirelli]

   Chris,

   There is quite a few messages in the list archives about the "issues" of
using nested objects.
   Best way is always to work with a "relational model" and assert all your
objects to the working memory. One example would be:

rule R1
when
    $o : Order( requestStatus == RequestStatus.ACCEPT )
    Message( state == MessageState.RELEASING, order == $o )
then
    // do something
end

    Having said that, if you don't think it is justifiable to assert all
objects into working memory because of just a few rules, you can also use
the "from" CE:

rule R2
when
    $m : Message( state == MessageState.RELEASING )
    Order( requestStatus == RequestStatus.ACCEPT ) from $m.getOrder()
then
     // do something
end

    Finally, version 4.0 final will allow you to write the rule the way you
wrote:

rule R3
when
    $m : Message( state == MessageState.RELEASING, order.requestStatus ==
RequestStatus.ACCEPT )
then
     // do something
end

   But it is important to note that the above will automatically generate an
embedded eval() for you, that is exactly the same as doing:

rule R4
when
    $m : Message( state == MessageState.RELEASING, eval(
order.getRequestStatus() == RequestStatus.ACCEPT ) )
then
     // do something
end

   And eval result needs to be constant over time.

   BTW, syntaxes used in R1, R2 and R4 are already supported in MR2/trunk.
Syntax used in R3 above will be available in Drools 4.0 final release.

   []s
   Edson

2007/6/6, Chris Mathrusse <christopher.mathrusse at sybase.com>:
>
> I'm new to the rules syntax and a bit frustrated with trying to learn it.
> I've
> reviewed the docs but keep running into the same issue. I have a parent
> object,
> Message, that contains an Order. An Order has a status that I want to
> test. So
> looking at the documentation and taking my best guess I've created a rule
> as
> follows:
>
> rule "Order not Accepted"
> when
>   $m : Message( state == MessageState.RELEASING, order.requestStatus ==
> RequestStatus.ACCEPT )
> then
>   ...
> end
>
> The problem is that when I start my application I get a compilation error.
>
> Caused by:
> org.drools.rule.InvalidRulePackage: [54,54]: unknown:54:54 mismatched
> token:
> [@423,1899:1899='.',<69>,54:54]; expecting type RIGHT_PAREN[54,94]:
> unknown:54:94 mismatched token: [@433,1939:1939=')',<37>,54:94]; expecting
> type
> LEFT_PAREN
>         at org.drools.rule.Package.checkValidity(Package.java:368)
>
>
> So what am I missing? I know it has to be something simple with my
> understanding
> of the syntax.
>
> Thanks for the help...
>
> _______________________________________________
> 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
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