[rules-users] Java5 Enum - Reference on usage in constraints.

[Edson Tirelli]

   Krishna,

   "this" is a special field that always refers to the fact itself, instead
of an attribute. Your use of "this" is fine.
   == used as a top level constraint evaluator always calls for the equals()
method on the object in question, or the appropriate comparator when dealing
with primitives.

  []s
  Edson

2008/1/31, Krishna Satya <krishna.ksatya at gmail.com>:
>
> Greetings.
> I am trying to find the correct approach to defining and using Java5
> Enum's in Drools constraints.
>
> *Psudo code:*
> Class RuleRequest {
>       ... other attributes ...
>       // RequestType is an enum type.
>       RequestType type ;
>
>       public RequestType getRequestType() {
>            return type;
>       }
> }
>
> public enum RequestType {
>    INTERNAL("internal"), EXTERNAL("external");
> }
>
> *Drools Rule:*
> # 1st Constraint - I could have listed the type in the constraint for
> RuleRequest but say I want that to be in a separate constraint
> # 2nd Constraint - on the nested RequestType enum
> *req: RuleRequest(..some match not based on the RequestType but other
> attributes of RuleRequest...)
> type: RequestType( ??? == RequestType.INTERNAL ) from req.requestType
> *
> What should be plugged in ??? to be able to match the requestType.
> Interestingly, if I say
> *type: RequestType( this == RequestType.INTERNAL ) from req.requestType  *when
> the ruleRequest has an RequestType of INTERNAL, the matching works.  But I
> do not see any examples/reference in the Drools documentation on the usage
> of "this" in constraints. I saw a posting from Edson T. using this which is
> why I tried it in the first place.
>
> *Question
> *- What is the expectation for the Enum.  Should it have methods (getters)
> that return the Enum type itself or methods that return the strigified value
> of the Enum?
> - What is syntax and usage practices for the usage of the "this" keyword
> - What really happens when the Drools engine does the == comparison on
> Enum's.  Does it convert to the string value of the enum and then compare
> that or is there something else in play.
>
> I hope I have asked valid questions as I see many questions relating to
> Enum but maybe a definitive/suggested approach and explanation from the
> drools dream team may serve as a good reference on this subject.
>
> Thanks.
> - Krishna
>
>
>
>
>
>
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>


-- 
  Edson Tirelli
  JBoss Drools Core Development
  Office: +55 11 3529-6000
  Mobile: +55 11 9287-5646
  JBoss, a division of Red Hat @ www.jboss.com
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