refactor-configuration.rb

# sandi
module GildedRose
  DEFAULT_CLASS = Item
  SPECIALIZED_CLASSES = {
    'normal'                  => Normal,
    'Aged Brie'               => Brie,
    'Backstage passes to ...' => Backstage
  }

  def self.for(name, quality, days_remaining)
    (SPECIALIZED_CLASSES[name] || DEFAULT_CLASS).new(quality, days_remaining)
  end 
end

# open for extension for configuration
class GildedRoseFactory < Struct.new(:specialized_classes, :default_class)
  def for(name, quality, days_remaining)
    specialized_classes.fetch(name, default_class).new(quality, days_remaining)
  end 
end

# usage

rose = GildedRoseFactory.new({
  'normal'                  => Normal,
  'Aged Brie'               => Brie,
  'Backstage passes to ...' => Backstage
}, Item)

rose.for #...