[rules-users] Accepted idiom for binding variable to restriction?

[Edson Tirelli]

   Syntactically speaking, I don't think the eval is necessary:

  $response : Response( $question : question, question.ID == "XYZ" )

   Behind the scenes Drools will still generate an eval to resolve the
nested property constraint, but the rule stays simple to read and maintain.

   Edson

2010/6/2 Wolfgang Laun <wolfgang.laun at gmail.com>

> The "inline eval" constraint is what you want: a boolean expression,
> within parentheses.
>
>   $response : Response( $question : question, eval(question.getID().equals(
> "XYZ" ) ) )
>
> See the Drools Expert manual, section on "Left Hand Side..."
>
> -W
>
>
> On 1 June 2010 23:54, Laird Nelson <ljnelson at gmail.com> wrote:
>
>> I have a fact that is inserted into my rule base.  It is a Response.
>>
>> A Response has a Question that it is a response to.  At the moment,
>> the Question itself is not separately inserted into the knowledge
>> base.  I would ideally like to keep it this way.
>>
>> What's the best approach for binding variables to both the Response
>> and its associated Question?
>>
>> That is, if the Question were inserted, it would be relatively easy:
>>
>> when
>>  $question : Question( )
>>  $response : Response( question == $question )
>>
>> ...but I'm finding myself somewhat confused how to "extract" a
>> Question out of a Response, particularly when, say, I want to "select"
>> only Responses whose associated Question IDs are "XYZ":
>>
>> when
>>  $response : Response( $question : question.ID == "XYZ" ) // boy
>> howdy does this seem wrong
>>
>> Is the easiest thing to do here to add a second rule that just inserts
>> the questions:
>>
>> when
>>  $response : Response
>> then
>>  insert($response.getQuestion())
>> end
>>
>> ...?  I would love to stay away from this if I could.
>>
>> Thanks,
>> Laird
>> _______________________________________________
>> rules-users mailing list
>> rules-users at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/rules-users
>>
>
>
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>


-- 
 Edson Tirelli
 JBoss Drools Core Development
 JBoss by Red Hat @ www.jboss.com
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