An example of the "Hexagonal Rails" concept from Matt Wynne

hexagonal_example.rb

# Tell, Don't Ask. 
# Easily plug in new listeners that respond to the API we have defined:
# create_succeeded, create_failed
# Benefits:
#   * Clean controller
#   * Small classes with single responsibilities
#   * Easy to test each individually
#   * No need for model-level callbacks, just plug in the relevant listeners
#   * No if statements - easy to follow logic

class ObjectController
  def create
    creator = ObjectCreator.new(self, ObjectFeedWriter.new, ObjectMailer.new)
    creator.create("Test 123")
  end
    
  def create_succeeded(name)
    puts "Controller: success (#{name})"
  end
  
  def create_failed(name)
    puts "Controller: failure (#{name})"
  end
end

class ObjectCreator
  attr_reader :listeners
  CALLBACKS = {
    "create" => {
      "true" => :create_succeeded,
      "false" => :create_failed,
    }
  }
  
  def initialize(*listeners)
    @listeners = listeners
  end
    
  def create(name)
    # Create the object, and *tell* the listeners what happened
    created = Object.create
    notify_listeners(CALLBACKS["create"][created.to_s], name)
    return created
  end
  
  def notify_listeners(callback, *args)
    listeners.each do |listener| 
      listener.send(callback, *args) if listener.respond_to? callback
    end
  end
end

class Object
  def self.create
    # Just for this example so we can run this and get success / failure randomly
    [true, false].sample
  end
end

class ObjectFeedWriter
  def create_succeeded(name)
    puts "Feed writer: success (#{name})"
  end
  
  def create_failed(name)
    puts "Feed writer: failure (#{name})"
  end
end

class ObjectMailer
  # Here, we can only respond to succeeded if we do not want to send mail in the case of a failure
  def create_succeeded(name)
    puts "Mailer: success (#{name})"
  end
end

ObjectController.new().create