gistfile1.rb

# abstracted code selection from tip.rb
# 'date_age' is named arbitrarily 

  def as_json(options = nil)
    methods = []
    methods << :can_upvote if @current_user_id.present?
    methods << :date_age
    super(methods: methods, include: { user: { only: :username } })
  end

  # calculate value to pass to JSON for availability in the partial
  def date_age
    time_ago_in_words(self.created_at)
  end