#---
# Excerpted from "The ThoughtWorks Anthology",
# published by The Pragmatic Bookshelf.
# Copyrights apply to this code. It may not be used to create training material, 
# courses, books, articles, and the like. Contact us if you are in doubt.
# We make no guarantees that this code is fit for any purpose. 
# Visit http://www.pragmaticprogrammer.com/titles/twa for more book information.
#---
# using method chaining the same as case 2 but with a model expression
# builder rather than a single object


ConfigurationBuilder.
  item(:secure_air_vent).

  item(:acid_bath).
    uses.acid.
       type(:hcl).
       grade(5).
    uses.electricity(12).

  item(:camera).uses.electricity(1).

  item(:small_power_plant).
    provides.electricity(11).
    depends_on(:secure_air_vent)