Drools variable binding: reassignment not allowed - drools

Question

Assume that MyObject is a Java Object with an integer property called integerProperty.
I would like to write a Drools rule like the following (syntactically incorrect):
rule "myRule"
when
MyObject( $integerProperty : integerProperty )
accumulate(
$o : MyObject(
integerProperty == $integerProperty + 1,
$integerProperty : this.integerProperty
);
$total : count($o);
$total > 10
)
then
[BLABLABLA]
end
I want to fire my rule when there is a set of more than 10 elements of type MyObject whose integerProperty values form an arithmetic sequence, e.g. 1, 2, 3, … In this case, I will assign a negative value to an HardMediumSoftLongScore object (hoping that information this helps).
I am sure that an MyObject having a given integerProperty is unique (eg. there is just one MyObject having integerProperty equal to, say, 2). The problem is that I'm not allowed to re-assign the variable binding $integerProperty. Is there a way around this?

Answer 1

Try implementing the below example and check whether you are getting your desired output. Before firing the rule insert the previous object as a global variable (prev in the example below) in the drool session.
global MyObject prev;
rule "myRule"
when
$total : Number(doubleValue > 10) from accumulate(
$o : MyObject( prev.getIntegerProperty() != null && $i : integerProperty == prev.getIntegerProperty() + 1),
init( double total = 0;),
action( total += 1; ),
reverse( total -= 1; ),
result( new Double( total ) ) )
then
[BLABLABLA]
end
In your java code before firing the rule set the previous object as a global object. Follow the code below :
kieSession.setGlobal("prev",myprevobject)
kieSession.insert(myobject)
kieSession.fireAllRules()