A topic-based, asynchronous MQTT handler

That's right, finally there's a mostly stable, connection-loss resistant MQTT handler out there that runs fully asynchronously. What's even nicer is that you can attach (and detach!) callbacks to any topic you want - including wildcards! Any topic can have as many callbacks as you want too, so don't worry about that!

That's great, but how to get it started?

The main code is simple:

require 'mqtt/sub_handler'

myClient = MQTT::Client.new(ADDRESS_OR_PARAMETERS); # See the "mqtt" gem for possible options!
mqttSubHandler = MQTT::SubHandler.new(myClient);    # Create a handler with a mqtt class

mqttSubHandler = MQTT::SubHandler.new('mqtts://Password:Username@Address') # Or use a string!
mqttSubHandler = MQTT.Eclipse(); # Or use the quick shortcut to 'iot.eclipse.org' for testing!

Subscribing

mySub = mqttSubHandler.subscribe_to "Any/Topic/You/Want" do |data, [topicMatch]|
    puts "I got some data: #{data}";
end
# Yup, it's that simple. The callback will be stored, and will run whenever data is received.

# You need to get rid of your subscription?
# Sure thing!

mqttSubHandler.unregister_subscription(mySub); # That'll remove the callback, and unsubscribe!
# Don't worry about breaking other subscriptions. The code checks if any other callbacks are attached to the topic in question!

Wildcard subscriptions

Wildcard subscriptions are also accepted with this code, and, may I say, are quite useful too!

mqttSubHandler.subscribe_to "A/Wildcard/+/Topic/+" do |data, topicList|
    puts "I got some data: #{data}"
    puts "The first + was: #{topicList[0]}"
    puts "The second one was: #{topicList[1]}"
end

Note: This also works with the "#" wildcard. Every following topic "branch" becomes a new array element!

Publishing

# Pushing gets easy, too:
mqttSubHandler.publish_to "Any/Topic/You/Want", theData, [qos: 1, retain: false]
# Right now, the code ONLY SUPPORTS QOS 0, AND WILL BLOCK!
# This is courtesy of the MQTT-Gem though, and nothing I can fix for now.

But ... Wait?

Yep, you can wait for data, too!

mqttSubHandler.wait_for "The/Waiting/Topic", [timeout: seconds or nil] do |data, [topicMatch]|
    # Confirm and process data here. The rest of the code will wait!
    # Return true when you found what you need, or set an optional timeout, and the main code will continue after that.
end

The same goes for the end of the code, if you have nothing else to run but want to keep listening:

mqttSubHandler.lockAndListen();
# This here also traps SIGINT, so you get a clean exit!