fetch4.rb

# If the comment tree exists in cache, it will be pulled from cache without
# doing any extra processing. If it doesn't exist in cache, we do all of the
# stuff I wrote about above.
data = Rails.cache.fetch(Comment.cache_key_for(@article, @params[:sort])) do
  arranged_comments.map do |data|
    # Each data object contains the comment, it's reply_to (if applicable), and
    # the comment children. Calling as_json will convert all of the data to a
    # plain JSON-like object.
    Api::V1::CommentSerializer.new(data).as_json
  end
end

# Once we have the comment data structure, we can pass it along to the decorator!
CommentDecoratorService.new(@article, data, current_member: @current_member).decorate!