[rules-users] Question on eval block

[Edson Tirelli]

   Inside eval() you write plain java code, where == is the identity
operator. When you write constraints, you are using DRL language where ==
calls .equals() method behind the scenes.

   []s
   Edson

2009/8/3 Shah, Malay <Malay.Shah at morganstanley.com>

>  Minor correction in the rule:
>
> The eval block is:
>
> eval(lastCapacity *=**=* null && entityOid == parentOid && msgType == "8")
>
> instead of
>
> eval(lastCapacity *!**= *null && entityOid == parentOid && msgType == "8")
>
> Any help is much appreciated.
>
> Thanks
>
> Malay Shah
>
>
>  ------------------------------
> *From:* Shah, Malay (IDEAS)
> *Sent:* Monday, August 03, 2009 4:18 PM
> *To:* rules-users at lists.jboss.org
> *Subject:* Question on eval block
>
>  Hi,
>
> I am trying to use eval block in one of the rules and am a bit confused
> about it. The rule is something like this:
>
>
> rule "LastCapacity"
> when
>     e: Execution(lastCapacity:lastCapacity,parentOid:parentOid)
>     eo:
> ExecutionOrder(entityOid:entityOid,msgType:msgType,execType:execType)
> *    eval(lastCapacity * *!**= null && entityOid == parentOid && msgType
> == "8")*
> then
>
> ..................
> end
>
> where Execution and ExecutionOrder are 2 objects that are linked by an ID.
> I expect eval to return true for certain sets of objects that I send. But,
> the above rule exits without running the consequence. On the other hand,
> when I write the rule as:
>
>  rule "LastCapacity"
> when
>     e: Execution(lastCapacity:*lastCapacity==null*,parentOid:parentOid)
>     eo: ExecutionOrder(entityOid:*entityOid == parentOid*, *msgType == "8"
> *)
> then
>
> .............................
> end
> the rule triggers the consequence for same set of objects. I thought that
> if the expression in eval block comes out to be true, the consequence will
> be triggered. Am I missing something obvious here?
>
> Thanks
>
> Malay Shah
>  ------------------------------
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-- 
 Edson Tirelli
 JBoss Drools Core Development
 JBoss by Red Hat @ www.jboss.com
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