Ruby 2.1 refinements

refine.rb

module TimeExtensions
  refine Fixnum do
    def min2sec; self * 60; end
  end
end
 
class Minutes
  using TimeExtensions

  def self.to_sec(min)
    min.min2sec
  end
end
 
puts Minutes.to_sec(2)  # => 120
puts 2.min2sec          # => NoMethodError