reference_object.rb

class MoneyUnique
  attr_accessor :pounds, :pence
  
  def initialize(pounds, pence)
    @pounds = pounds
    @pence = pence
  end
end

four_quid = MoneyUnique.new(4, 0)
three_quid = MoneyUnique.new(3, 0)
four_quid_again = MoneyUnique.new(4, 0)

puts (four_quid == three_quid)  # => false, good!
puts (four_quid == four_quid_again)  # what does this print?

value_object.rb

class Money
  attr_accessor :pounds, :pence
  
  def initialize(pounds, pence)
    @pounds = pounds
    @pence = pence
  end
  
  def ==(other)
    other.pounds == pounds && other.pence == pence
  end
  
  alias_method :eql?, :==
end

# Now let's try the same code again, but using the class that provides its own
# equality logic
four_quid = Money.new(4, 0)
three_quid = Money.new(3, 0)
four_quid_again = Money.new(4, 0)

puts (four_quid == three_quid)  # => false, good!
puts (four_quid == four_quid_again)  # what does this print?