How to pass a custom comparator to “sort”?

Question

Class A has the following comparator:

class A
  attr_accessor x

  def my_comparator(a)
    x**2 <=> (a.x)**2
  end
end

Answer 1

items.sort!(&:my_comparator)

This calls the :my_comparator.to_proc internally, which returns a block

proc {|x,y| x.my_comparator(y)}

thus reducing this answer to Ben Alpert's answer.

(But I agree with Phrogz's observation that if this is the natural order for the class, then you should use the Tin Man's answer instead.)