Nicer Ruby Singleton

singleton.rb

class SingletonTest
  def data
    @data
  end

  def data=(n)
    @data = n
  end

  @old_new_method = self.method(:new)

  def self.new
    @instance ||= @old_new_method.call
  end
end

a = SingletonTest.new
a.data = 6
b = SingletonTest.new
puts b.data