DP: Fabric Class

ruby_fabric.rb

class Blog
  attr_writer :post_source

  def new_post
    post_source.call.tap do |p|
      p.blog = self
    end
  end

  private
    ##
    ## fabric pattern
    ##
    def post_source
      @post_source ||= Post.public_method(:new)
    end
end

class Post
  ##
  ## dependency injection pattern
  ##
  def publish(clock = DateTime)
    self.pubdate = clock.now blog.add_entry(self)
  end
end