Signals

A light weight publish / subscribe. It is similar to how the Wisper gem works. Except that listeners must include Signals::Subscriber so that it can have a nice DSL and listen for specific events and trigger actions based on those events. This library also has no external dependencies.

Installation

gem 'signals'

Usage

require 'signals'

class Coach
  include Signals::Publisher
end

class Player
  include Signals::Subscriber

  listen_for :v_formation => :run
  listen_for [:hat_trick, :v_formation] => :audible
  listen_for :stop => [:look, :run]
  listen_for :stop => :audible

  def initialize(name)
    @name = name
  end

  def run(coach)
    puts "#{@name} is running"
  end

  def audible(coach)
    puts "#{@name} is calling an audible"
  end

  def look(coach)
    puts "#{@name} is looking"
  end
end

coach   = Coach.new
forward = Player.new('John')
center  = Player.new('Jeff')

coach.subscribe(forward)
coach.subscribe(center)

coach.on(:stop) do |c|
  puts "I'm telling you to stop"
end

coach.broadcast(:v_formation, coach)
coach.broadcast(:hat_trick, coach)
coach.broadcast(:stop, coach)

Rails Usage

# app/controllers/something_controller.rb
class SomethingController < ApplicationController
  # ...
  def create
    service = CreateSomething.new(something_params)
    service.subscribe(AListener.new)
    service.subscribe(AnotherListener.new)
    service.on(:create_something_successful) do |something|
      redirect_to something_path(something)
    end
    service.on(:create_something_failed) do |something|
      @something = something
      render action: 'new'
    end
    service.execute
  end
  # ...
end

# app/services/create_something.rb
class CreateSomething
  include Signals::Publisher

  def initialize(something_params={})
    @something = Something.new(something_params)
  end

  def execute
    if @something.save
      broadcast(:create_something_successful, @something)
    else
      broadcast(:create_something_failed, @something)
    end
  end
end

# app/listeners/a_listener.rb
class AListener
  include Signals::Subscriber

  listen_for :create_something_success => :enqueue_send_email

  def enqueue_send_email
    # queue it up to send an email
  end
end

# app/listeners/another_listener.rb
class AnotherListener
  include Signals::Subscriber

  listen_for :create_something_failed => :log_failure

  def log_failure(something)
    Rails.logger.error "Something failed"
  end
end

Contributing

1. Fork it
2. Create your feature branch
3. Commit your changes
4. Write tests for those changes
5. Push the changes
6. Create new Pull Request