Dynamic Rule Results

Hi

Is it possible to construct dynamic rule result. For example could

event: { 
    type: 'honor-roll',
    params: {
      message: 'Student made the athletics honor-roll'
    }
  }

message parameter be constructed in the runtime?

[MattCopenhaver]

@waglik I think what you’re describing is more of a Dynamic Event rather than a Dynamic Rule Result.

Accessing the almanac or factResult within onSuccess should do the trick. Your onSuccess function will have to contain the logic of how to build the dynamic events/results.

onSuccess: https://github.com/CacheControl/json-rules-engine/blob/master/docs/engine.md#engineonsuccess-functionobject-event-almanac-almanac-ruleresult-ruleresult Usage of Alamanc within an onSuccess: https://github.com/CacheControl/json-rules-engine/blob/master/docs/almanac.md#retrieve-fact-values-when-handling-events Rule Result (contains factResult): https://github.com/CacheControl/json-rules-engine/blob/master/docs/rules.md#rule-results

[CacheControl]

Can an event be decorated onSuccess like below without the added parameters getting permanently added to the rule?

Couple options here to avoid event mutation impacting other engine runs:

1. You could have a data structure outside of the engine scope that tracks the state, e.g.:

let newEvent
engine.on('success', function(event, almanac, ruleResult) {
  newEvent = cloneDeep(event)
  newEvent.params.newProp1 = "decoration 1";
})

1. if you’d prefer to keep things more internal to the engine itself, you could use almanac.addRuntimeFact() to save state and then retrieve it from the almanac later after run() completes:

engine.on('success', function(event, almanac, ruleResult) {
  newEvent = cloneDeep(event)
  newEvent.params.newProp1 = "decoration 1";
  almanac.addRuntimeFact('new-event', newEvent)
})
const {almanac} = engine.run();
await almanac.factValue('new-event')