Open/Closed Example in #Ruby

01_news_digest_broadcaster.rb

require 'active_support/inflection'
Dir["./path/to/broadcasters/*.rb"].each {|broadcaster| require broadcaster }

module NewsDigestBroadcaster
  extend self
  def broadcast(user, preference)
    broadcaster = Object.const_get("#{preference.capitalize}NewsDigestBroadcaster")
    broadcaster.(user, news_digest)
  end
  alias_method :call, :broadcast
  
private

  def news_digest
    # logic to collect and build the news digest collection
  end
end

02_email_news_digest_broadcaster.rb

module EmailNewsDigestBroadcaster
  extend self
  def email(user, news)
    send_email(user, news)
  end
  alias_method :call, :email

private

  def send_email(user, news)
    # send the email
  end
end

03_im_news_digest_broadcaster.rb

module ImNewsDigestBroadcaster
  extend self
  def im(user, news)
    send_im(user, news)
  end
  alias_method :call, :im

private

  def send_im(user, news)
    # send the instant message
  end
end

04_tweet_news_digest_broadcaster.rb

module TweetNewsDigestBroadcaster
  extend self
  def tweet(user, news)
    send_tweet(user, news)
  end
  alias_method :call, :tweet

private

  def send_tweet(user, news)
    # send the tweet
  end
end