Is there a way to get the rule name from within a rule?

[djg2002]

I would like to pass rule names to my functions which I can do with a string but its fragile.

Is there an object I can reference from within a rule that contains the current rule/context? This would be really useful for establishing where behaviour is coming from.

Thanks

[tlaraMQ]

I agree and I think I want to do the same thing. Is it possible to retrieve the name of the activated rule?

[ivoshm]

As I know, it's different in 'when' and 'then' section of the rule:

• in 'then' section you can implement method EvaluateRuleEntry() in GruleEngineListener interface and store entry.RuleName in any accessible variable
• in 'when' section you face too aggressive caching - method getting RuleName is called only once for a fact and so it returns name of the first evaluated rule until the end of the cycle

[tlaraMQ]

Thank you for your answer. In my case is the 'then' section. I think @djg2002 's is the 'when' section.

Could you elaborate on the GruleEngineListener interface and the EvaluateRuleEntry() method? I do not see any documentation regarding it.

[ivoshm]

I use it like this:

type RuleMachine struct {
        ...
	state        *RuleState
        ...
}

type RuleState struct {
        ...
	RuleName   string
        ...
}

func (r *RuleMachine) EvaluateRuleEntry(cycle uint64, entry *ast.RuleEntry, candidate bool) {
	if candidate {
		r.state.RuleName = entry.RuleName
	}
}

If you publish the instance of RuleState in the dataContext (something like dataContext.Add("S", r.state)) then you can get property S.RuleName in the rule.

Basic documentation of GruleEngineListener is available in source code:
https://github.com/hyperjumptech/grule-rule-engine/blob/master/engine/GruleEngineListener.go

I apologise for the brevity, but I hope this is understandable.

[ivoshm]

One more idea ... if you need RuleName only in "then" section it's enough to implement method ExecuteRuleEntry() like

func (r *RuleMachine) ExecuteRuleEntry(cycle uint64, entry *ast.RuleEntry) {
	r.state.RuleName = entry.RuleName
}

and don't "mess" with EvaluateRuleEntry()

[ivoshm]

But this whole approach is a hack - surely it could be done more elegantly and reliably inside GRL engine.

[tlaraMQ]

Thank you for your insights, I'll check if I can implement the approach