[rules-users] Issues Regarding use " Eval"

[Edson Tirelli]

   Eval's are indeed less performatic than any other type of constraints.
"inline-evals" are not as bad, but are also heavier than regular
constraints.
   The recommendation is to avoid when possible, but for some cases it is
not possible.

   If you are using MR3 or later, you can use MVELs syntax in your
constraints:

when
   MyClass( aMapAttribute['aKey'] == "some Value" )
then
   ...
end

    The above will transparently be translated to an inline-eval, but that
is the best you can do when working with maps.

    []s
    Edson


2007/7/2, Rajesh_Kumar <Rajesh_Kumar at rsystems.com>:
>
> Hi all,
>
> I want to use "eval" in my rules, but in rule writing guidelines Mark
> has
> Written that "Eval is Evil".
>
> I want to compare the values of Hash Map in my when (conditions) part.
>
> 1) Will anyone suggest something so that I can compare Hash Map keys in
> when part?
>
> 2) Does is there any performance related issue related to "eval";
>
> Regards
>
> Rajesh
>
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-- 
  Edson Tirelli
  Software Engineer - JBoss Rules Core Developer
  Office: +55 11 3529-6000
  Mobile: +55 11 9287-5646
  JBoss, a division of Red Hat @ www.jboss.com
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