How can I get an MQTT thing/channel's "commandTopic" from a rule?

[rlkoshak (Rich Koshak)]

@jimtng

However I’d like to get the triggering item’s commandTopic from within the rule. Is this possible?

Triggering Item? No. Channel trigger? Yes.

I have no idea how to define this using .things files (the original developer recommends against .things files so I don’t use them for MQTT). But in PaperUI you can create a Channel on the Broker Thing and there is an option to include the MQTT topic and message on the receivedEvent implicit variable. See Marketplace MQTT Event Bus for an example.