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:

http://github.com/mojombo/erlectricity

To get all of the dependencies, install the gem first. The best way to get your changes merged back into core is as follows:

1. Clone down your fork
2. Create a topic branch to contain your change
3. Hack away
4. Add tests and make sure everything still passes by running rake
5. If you are adding new functionality, document it in the README.md
6. Do not change the version number, I will do that on my end
7. If necessary, rebase your commits into logical chunks, without errors
8. Push the branch up to GitHub
9. Send me (mojombo) a pull request for your branch

Copyright

Copyright (c) 2009 Scott Fleckenstein and Tom Preston-Werner. See LICENSE for details.