[rules-users] How to check for a variable number of "conditions" in a rule?
Greetings!
I want to create a rule that checks a fact which contains an array to see if n or more of
the elements of that array have a specific value. The number of elements to check will
vary from invocation to invocation of the rules engine and will likely be added as a
global.
I can do this by using a helper function. Say, for example, I have:
rule "fire_when_testFlags_true"
when
eval(testFlags(flags, limit.intValue()));
then
System.out.println("Yup, " + limit + " or more flags are
true!");
end
Where flags and limit are both globals. Then I can define testFlags as:
function boolean testFlags(Flags flags, int threshold) {
int count = 0;
for(int i=0; i < flags.getSize(); i++) {
if (flags.getValue(i)) {
count++;
if (count>= threshold) {
return true;
}
}
}
return false;
}
This works but violates the warning not to use a global that isn't immutable in the
LHS of a rule. Does anyone have an idea about how to implement a rule that in effect has
an arbitrary number of conditions to be tested?
Ron
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