[rules-users] How to write a rule that fires when it matches against specific facts in working memory.

[groovenarula]

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] [mailto:ml-node+2380361-572428564-9505 at n3.nabble.com]
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
	
	Â  Â  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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