Railsy callback style

publishes_posts.rb

class PublishesPosts < Struct.new(:post_id, :ui)

  def run
    Blog.lookup_post(post_id) do |result|
      result.success => lambda {|post| post.publish; ui.post_published(post) },
      result.failure => lambda {|post_id| ui.no_such_post(post_id) })
    end
  end

end