require 'moosex'


module Eq
	include MooseX.disable_warnings()

	requires :equal

	def no_equal(other)
		! self.equal(other)
	end
end

module Valuable
	include MooseX

	has value: { is: :ro, requires: true } 
end	

class Currency
	include Valuable
	include Eq  # will warn unless disable_warnings was called.
                # to avoid warnings, you should include after  
	            # define all required modules,

	def equal(other)
		self.value == other.value
	end

	# include Eq            # warning safe include
end

class Comparator
	include MooseX

	has compare_to: { 
		is: :ro,
		isa: Eq,
		handles: Eq, 
	}
end

module Wrapper
	include Eq
end

class WrongClass
	include Wrapper

	has one: { is: :rw }
end

c1 = Currency.new( value: 12 )
c2 = Currency.new( value: 12 )
c3 = Currency.new( value: 24 )

c1.equal(c2) # true
c1.equal(c3) # false

Comparator.new(compare_to: c1).no_equal(c2) # false
Comparator.new(compare_to: c1).no_equal(c3) # true

WrongClass.new(one: 1, two: 2) # will raise exception