Ruby get reference to a singleton class of object

class Object
  class << self
    def self_class
      self
    end
  end

  def singleton_class
    class << self
     self
    end
  end
end
a = [1,2,3]
p a
puts Array.self_class
puts a.singleton_class
 
E:\>ruby singleton_class.rb
[1, 2, 3]
Array
#<Class:#<Array:0x294053c>>