lambdas in ruby case (switch)

A little class that has code and message attributes (ignore the bizarre HTML link, I can't prevent Markdown from putting it in?):

class Response
  attr :code, :message
  def initialize(c, m)
    @code, @message = c, m # the <a> should not be here...
  end
end

...and a method that analyzes those attributes. The interesting part is in a case, where two of the whens use some local methods that return lambdas:

def analyze(resp)
  def code_is(c)
    lambda { |r| r.code == c }
  end

  def message_is(m)
    lambda { |r| r.message == m }
  end

  case resp
  when code_is(200)
    "we are good to go"
  when message_is("Not Modified")
    "not a 200, but it's okay anyway"
  else
    "uh oh, we got a problem... #{resp.inspect}"
  end
end

Now let's see it in action:

response = Response.new(200, "whatever")
puts "first up", analyze(response), ""

response = Response.new(300, "Not Modified")
puts "next", analyze(response), ""

response = Response.new(404, "No Way")
puts "and finally", analyze(response)

This works because the whens do a ===, which lambdas/Procs use to run themselves.

More: http://www.aimred.com/news/developers/2008/08/14/unlocking_the_power_of_case_equality_proc/