Regis,
You are probably having problems with mutable predicates, when using "
subject.allocatedDays". As a first step to understand your problem, I
strongly encourage you to make constraints flat, i.e., avoid using nested
accessors. After you get used to what can and what can't be done, you can go
back to use nested accessors.
Also, I suggest you use modify() block instead of update():
*
rule
*"allocate"
*when*
$lesson : Lesson(allocated == *false*, session.type == Session.DISTINCT )
$subject : Subject( $allocatedDays : allocatedDays ) from $lesson.subject
$availableHour : Hour(allocated == *false*, day *not* *memberOf*$allocatedDays)
*then*
modify( $lesson) {
setHour($availableHour ),
setAllocated(*true*)
}
modify( $availableHour )
setSubject($lesson.getSubject()),
setAllocated(*true* )
}
**
*end*
Hope it helps.
[]s
Edson
2008/4/14 Piccand, Regis <rpiccand(a)verisign.com>:
Hi all,
I am evaluating Drools and am stuck with a simple rule that selects
elements which do not correspond to the condition... Since I am updating
objects in the RHD, I guess it has to do with my wrong understanding (and
the cache...?)
I am trying to allocate lessons to periods (hour). My object model can be
summarize is as follows :
Lesson
boolean : allocated // true if the lesson has been allocated to an
hour
int : session // a session is a bunch of lessons
Subject : subject // an allocated lesson is assigned a subject
Subject
Set<Day> : allocatedDays // days in which this subject is taught -
checked before allocation, as a subject can only be taught once a day
Hour
boolean : allocated // true is this hour has been allocated with a
lesson
Day : day // the day this hour belongs to - required to check with
subject.allocatedDays
I put in the workingMemory a bunch of Lesson objects, which have been set
with Subject and Session id. I also put a bunch of Hour object, set with a
Day.
My rule is as follows:
*
rule
* "allocate"
*when*
$lesson : Lesson(allocated == *false*, session.type == Session.DISTINCT,
$allocatedDays : subject.allocatedDays)
$availableHour : Hour(allocated == *false*, day *not* *memberOf*$allocatedDays)
*then*
$lesson.setHour($availableHour ) ;
$lesson.setAllocated(*true*) ;
*update*($lesson);
$availableHour.setSubject($lesson.getSubject()) ;
$availableHour.setAllocated(*true* );
*update*($availableHour);
*end*
When I set a debug on the first line of the THEN section, I can see that
sometimes $availableHour.allocated == true ... sometimes $lesson.allocated
== true (although it's an implicit And statement ...)
Therefore, I can see that the update() works, but it seems that the rule
does not use the updated object (due to shallow copy ??)
Any help more than welcome
Regis
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Edson Tirelli
JBoss Drools Core Development
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