Erlectricity

http://github.com/mojombo/erlectricity

By Scott Fleckenstein, Tom Preston-Werner

Development Status: Production/Stable

Description

Erlectricity allows a Ruby program to receive and respond to Erlang messages sent over the Erlang binary protocol.

Install

$ gem install erlectricity

-or-

$ gem install mojombo-erlectricity -s http://gems.github.com

The Simplest Example

Ruby side (echo.rb)

require 'rubygems'
require 'erlectricity'

receive do |f|
  f.when([:echo, String]) do |text|
    f.send!([:result, "You said: #{text}"])
    f.receive_loop
  end
end

Erlang side (echo.erl)

-module(echo).
-export([test/0]).

test() ->
  Cmd = "ruby echo.rb",
  Port = open_port({spawn, Cmd}, [{packet, 4}, nouse_stdio, exit_status, binary]),
  Payload = term_to_binary({echo, <<"hello world!">>}),
  port_command(Port, Payload),
  receive
    {Port, {data, Data}} ->
      {result, Text} = binary_to_term(Data),
      io:format("~p~n", [Text])
  end.

Data Type Conversions and Matching

% Port is the port opened via open_port({spawn, Cmd}, [{packet, 4}, ...])
% Message is the Erlang term to encode and send to the port
send(Port, Message) ->
  port_command(Port, term_to_binary(Message)).

# Each triplet below represents:
# (line 1) the Erlang call
# (line 2) the Ruby matcher
# (line 3) the Ruby output

send(Port, test).
f.when(:test) { p :ok }
# :ok

send(Port, {atom, symbol}).
f.when([:atom, Symbol]) { |sym| p sym }
# :symbol

send(Port, {number, 1}).
f.when([:number, Fixnum]) { |num| p num }
# 1

send(Port, {string, <<"foo">>}).
f.when([:string, String]) { |str| p str }
# "foo"

send(Port, {array, [1,2,3]}).
f.when([:array, Array]) { |arr| p arr }
# [1, 2, 3]

send(Port, {array, [<<"abc">>, <<"def">>]}).
f.when([:array, Array]) { |arr| p arr }
# ["abc", "def"]

send(Port, {hash, [{key,val}]}).
f.when([:hash, Erl.hash]) { |hash| p hash }
# {:key=>:val}

send(Port, {object, {1,{2},3,<<"four">>}}).
f.when([:object, Any]) { |any| p any }
# [1, [2], 3, "four"]

Contribute

If you'd like to hack on Erlectricity, start by forking my repo on GitHub: