Edson,

That worked beautifully !

Drools is looking more and more promising for what we need to do.

Thanks for all your help,

Gurvinder


-----Original Message-----
From: Edson Tirelli-4 [via Drools - Java Rules Engine] [[hidden email]]
Sent: Sat 1/29/2011 10:59 PM
To: Gurvinder Narula1
Subject: Re: How to write a rule that fires when it matches against specific facts in working memory.


   Up to Drools 5, the accumulate function API supports only a single argument to the function, but that argument can be an array or a list. So what I do on my own implementations is to pass the $param as one element of the array and $o as the other. It is not ideal, but it is how you can do that in Drools 5. In Drools 6 I will change the API to support multiple parameters, but I've been postponing that because when I do it, it will break existing implementations of the interface.

   Anyway, if you are using the MVEL dialect, creating a list is as simple as wrapping it in [ ], as you could see in my previous e-mail.

$options : List() from accumulate(Â
      $op : Option(),
      matchAll( [ ${param}, $op ] ) )

    Edson

2011/1/29 groovenarula <[hidden email]>



        Edson,
       
        I did manage to use the 'CollectSetAccumulateFunction' as a template for the
        MatchAll and have also successfully 'called' the accumulate function from a
        rule written in a .drl file. But I'm stuck at one point - how to send the
        value of $param to the accumulate method ? From what I understand, the
        accumulate method is invoked for each fact - so if I write
       
            MatchAll( $o ) it will invoke the accumulate method and passing $o fact
        to the method via the 'Object value' parameter.
       
        So far so go, however, I'm stuck on how to pass the value of '$param' to the
        accumulate method (or any other method like init, getResult for that
        matter).
       
        One option I can think of is to change the definition of the Option fact to
        include a 'param' field and then write a rule that sets the value of that
        field to $param (so every Options param field would get set to the value of
        $param). I can then extract that in the accumulate method it self. But is
        there a better way that I might be missing ?
       
        Thanks in advance,
        Gurvinder
       
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--
  Edson Tirelli
  JBoss Drools Core Development
  JBoss by Red Hat @ www.jboss.com


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