Armstrong numbers

armstrong.rb

class Integer
  def to_a
    n = []
    x = self
    while x > 0
      n << x.modulo(10)
      x -= n.last
      x /= 10
    end
    n.reverse
  end

  def armstrong?
    self == self.to_a.map { |x| x**self.to_s.length }.inject(:+)
  end
end

It probably isn't the fastest solution but a pretty one in my (noobish) opinion.