phone.rb

require 'phony'


Phone = Struct.new(:value) do
  alias_method :value, :to_s
  
  def initialize(value)
    @value = value.to_s
  end
  
  def plausible?
    Phony.plausible? @value
  end
end

user.rb

class User
	composed_of :phone, class_name: 'Phone', 
    mapping: %w(phone value), allow_nil: true
end