MQTTMatcher

MQTTMatcher allows for defining functions to match MQTT topics.

It turns

use MQTTMatcher
match "a/+b/#", payload, _args do
  IO.inspect(b)
  IO.inspect(rest)
end

into this:

def match(path, payload, args \\ nil) do
  path
  |> String.split("/")
  |> int_mqtt_match(args)
end

defp int_mqtt_match(["a", b | rest], payload, args) do
  IO.inspect(b)
  IO.inspect(rest)
end

The variables defined in the MQTT topic with a beginning + are turned into Elixir variables, the ‘#’ is turned into a tail matching list. All matches are defined as private functions and a wrapper function is created to call those functions, splitting the input MQTT topic and passing payloads as well as generic (optional) arguments.

Matching rules

MQTTMatcher uses the following rules to expand the parts of the part to Elixir code:

Please note that repeating a named path pattern (foo/+bar/+bar) means that the pattern must repeat the same way to match. This means foo/test/test would match the given pattern, foo/bar/baz would not.

Installation

If available in Hex, the package can be installed by adding mqtt_matcher to your list of dependencies in mix.exs:

def deps do
  [
    {:mqtt_matcher, "~> 0.1.0"}
  ]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/mqtt_matcher.