gistfile1.rb

# Offering from lee:

class NarrativeController
 class << self
  def next_collaberator_for(story)
      raise ArgumentError "Require an instance of Story" unless story.is_a? Story
      collab_ids = story.collabs.map(&:id)
      last_collab_id = story.fics.collabs.last.collab_id
      last_collab_index = collab_ids.index(last_collab_id) || -1
      next_collab_id = collab_ids[last_collab_index + 1]
      Collab.find_by_id(next_collab_id)
  end
 end
end

# This works out who's the next collaborator to write a Fic on a given story.
# This would work well as an instance method on the Story Controller.
# Also, an Observer to watch for saves could use this after a Fic is saved in order to notify the next collaborator that it is their turn to write.