Re: [rules-users] Chart notation, update, and infinite loops
Greg,
1) Yes, in this case I'm looking for the cartesian join.
2) No, I can't add a property to Charge as it's part of our corp Object
Model.
However, I could create a third object that manages whether the Charge has
been processed which works just fine. Unless there is a simpler strategy /
technique, I'll go with that.
Do you know of any way to keep the rule from being put back on the agenda
when amountFact is updated? I want other rules to know that it's been
updated, just not the rule that made the change.
Dan
Greg Barton wrote:
1) Do you want to apply all Charges in working memory to all "Amount"
Facts? I ask because the rule is a cartesian join (i.e. no relation
between matched objects) and that sometimes performs in ways users don't
expect. (i.e. all combinations of objects that match the conditions are
affected by the rule)
2) Can you add a property to the Charge object? Then you could use a
boolean named "applied" to prevent future matches.
Rule "Update Amount"
when
amountFact : Fact(name == "Amount")
charge : Charge(applied == false)
then
Double amount = amountFact.getAmount();
Double chargeAmount = charge.getAmount();
amountFact.setAmount(amount + chargeAmount);
update(amountFact);
charge.setApplied(true);
update(charge);
end
If a charge could be applied to multiple Facts you could maintain an
"appliedTo" list of Facts in the Charge, and check that instead of a
simple boolean.
--- On Tue, 11/4/08, Dan Seaver <dan.seaver(a)ge.com> wrote:
> From: Dan Seaver <dan.seaver(a)ge.com>
> Subject: [rules-users] Chart notation, update, and infinite loops
> To: rules-users(a)lists.jboss.org
> Date: Tuesday, November 4, 2008, 11:50 AM
> I'm trying to find a good technique for updating
> specific facts in working
> memory. What I'm currently doing is something like
> this:
>
> Rule "Update Amount"
> when
> amountFact : Fact(name == "Amount")
> charge : Charge()
> then
> Double amount = amountFact.getAmount();
> Double chargeAmount = charge.getAmount();
> amountFact.setAmount(amount + chargeAmount);
> update(amountFact);
> end
>
> The update statement causes an infinite loop.
> I tried using no-loop, which works if there is 1 charge,
> but not if there
> are more than one.
>
> Any help with solutions or strategies would be much
> appreciated.
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