Re: [rules-users] Date arithmetic in “when†session
Michael,
Just an important note, that sometimes is overlooked by users:
*** Inline evals and return value predicates MUST be time constant ***
It means that an inline eval() must return the exact same value if it is
executed now, or in 5 minutes from now, or whatever. So, it is not advisable
for you to write the constraint as you did.
The correct way would be to use a top level eval() that does not suffer
from the same restriction:
MyFact( $value : value )
eval( $value.before(DateHelper.getModifiedDate(-6, "MONTHS")))
The use of a non-time-constant inline eval (or return value predicates)
causes unpredictable behavior in the engine.
[]s
Edson
2008/5/7 Michael B. <michael.bain(a)mckesson.com>:
I dont know if this is still outstanding since the original post seems to
have disappeared, but this is what I did during my proof of concept that I
am going through:
In a helper class (i.e. DateHelper) I had this method:
public static Date getModifiedDate(int amount, String unit) {
Calendar cal = Calendar.getInstance();
cal.setTime(getNow());
BusinessObject.stripTime(cal);
int calUnit = Calendar.DAY_OF_YEAR;
if (UNIT_MONTHS.equals(unit))
calUnit = Calendar.MONTH;
else if (UNIT_YEARS.equals(unit))
calUnit = Calendar.YEAR;
cal.add(calUnit, amount);
return cal.getTime();
}
Then in my rule it would be like this:
MyFact( eval( value.before(DateHelper.getModifiedDate(-6, "MONTHS"))))
Hope that helps.
-----
Drools Noob since 5/2008
--
View this message in context:
http://www.nabble.com/Re%3A-Date-arithmetic-in--%C3%A2%C2%80%C2%9Cwhen%C3...
Sent from the drools - user mailing list archive at Nabble.com.
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
--
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
Attachments:
- attachment.html (text/html — 3.3 KB)