switch.rb

# In response to:
# http://mlomnicki.com/ruby/tricks-and-quirks/2011/02/10/ruby-tricks2.html
# Ruby 1.9.2 has some neat stuff that lets us make a readable
# alternative case statement that calls each method in turn.

# 1.9.2 features used:
#   * hashes are ordered in 1.9.2
#   * cool JSON-style hash syntax
#   * concise lambda syntax

module Kernel
  def switch(thing, hash)
    hash.each do |method, proc|
      return proc[] if method == :else || thing.send(method)
    end
  end
end

switch offer,
  available: -> { order.submit },
  cancelled: -> { order.reject },
  postponed: -> { order.postpone },
  else:      -> { raise UnknownStateError.new }