Fancy sort in ruby

sort.rb

Animal = Struct.new(:name, :height, :legs)
animals = [
  Animal.new('dog', 10, 4),
  Animal.new('cat', 5, 4),
  Animal.new('snake', 2, 0),
  Animal.new('sloth', 5, 4),
  Animal.new('ant', 1, 6)
]

ASCENDING = 'ascending'
DESCENDING = 'descending'

class Order < Struct.new(:order, :value)
  def <=>(other)
    if order == ASCENDING
      value <=> other.value
    else
      other.value <=> value
    end
  end
end

def sort(values, key, order=ASCENDING)
  values.sort_by { |value| Order.new(order, value.send(key)) }
end

puts sort(animals, 'name', DESCENDING)