[rules-users] Comparing Strings (sort order)

[Darko Ivancan]

Hi Charles,

This sounds rather like a JAVA question, but well

1. You should use the compareTo method, inherited from Comparable.

2. about the rules itself, it should be more something like
$A1 : ActionArchive($mp1 : mediaPool);
$A2 : ActionArchive(this != $A1,  mediaPool.compareTo($mp1) < 0);

3. Having a huge number of actionArchives, you might want to consider storing them as an arra in a global variable and using the from operator in your rule.

Hope this helps,
Darko


-------- Original-Nachricht --------
> Datum: Thu, 03 Jul 2008 17:17:51 -0500
> Von: Charles Binford <Charles.Binford at sun.com>
> An: rules-users at lists.jboss.org
> Betreff: [rules-users] Comparing Strings (sort order)

> I'm trying to figure out how to compare strings in drools.  I'd prefer 
> to just be able to say something like:
> when
>   obj(member > "string")
> ....
> 
> This doesn't work because the > or < operations are not allowed (though 
> I saw in a May 6th post Edson gave a pointer to how to add it.)  Next I 
> tried using eval().  Based on everything I've read this should work.  My 
> problem is getting the syntax correct.  My object "ActionArchive" has a 
> member called "mediaPool".  I'd like to choose the one with the lowest 
> (alphabetically) mediaPool string.
> 
> Try one.....
> rule "testme"
>     when
>         $ar : ActionArchive($mp : mediaPool)
>         not (eval (ActionArchive(getMediaPool().CompareTo($mp)) < 0))
>     then
>         System.out.println("low mp= " + $ar.getMediaPool());
> end
> -----------
> Rule Compilation error : [Rule name=junk, agendaGroup=MAIN, salience=0, 
> no-loop=false]
>     rules/Rule_testme_0.java (8:997) : The method getMediaPool() is 
> undefined for the type Rule_junk_0
> 
> 
> Try two......
> rule "testme"
>     when
>         $ar : ActionArchive($mp : mediaPool)
>         not (eval (ActionArchive(mediaPool.CompareTo($mp)) < 0))
>     then
>         System.out.println("low mp= " + $ar.getMediaPool());
> end
> -----------
> Rule Compilation error : [Rule name=testme, agendaGroup=MAIN, 
> salience=0, no-loop=false]
>     rules/Rule_testme_0.java (8:999) : mediaPool cannot be resolved
> 
> Thanks for any pointers.
> Charles
> p.s. consider this a vote for adding > < support for Strings....
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