I wonder if you can use a Global (or a static variable) to do the same without really changing your rule.

Something like this.

Global Integer ruleFired;

rule "try not to loop"
   when
        $a : A($code : code)
        $b : B(parentCode == $code)
   then

if(ruleFired != 1)

{
addResult($a, $b);

Drools.getWorkingMemory().setGlobal(“ruleFired”,1);

}
end

From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Maxim Veksler
Sent: Monday, January 26, 2009 5:52 PM
To: Rules Users List
Subject: [rules-users] Not looping the rule when more then 1 valid match is found

Hello group,

Assuming I have the rule:

rule "try not to loop"
   when
        $a : A($code : code)
        $b : B(parentCode == $code)
   then
        addResult($a, $b);
end

and the classes:

public class A {
int code;
}

public class B {
int parentCode;
}

I insert into the WM 4 objects :
A(code = 1), A(code = 2);
B(parentCode=1), B(parentCode = 2);

I would like that after calling fireAllRules() only 1 match will be returned. I have no preference regarding which one, in the current situation 2 matches are returned.

Anyone could suggest a method to enforce this ?

Thank you,
Maxim.