ArmstrongNumbers in Ruby

def armstrongNumber n
  a = n.to_i
  n = n.to_s
  digits = n.length
  array = Array.new
  n.each_char {|c| array.push(c.to_i)}
  array_cubo = array.map do |valore|
    (valore.to_i)**digits
  end
  sum = 0
  array_cubo.each { |a| sum+=a }
  if sum == a
    puts "#{sum} is an Armstrong number."
  end
end

puts 'Please insert an integer'
num = gets.chomp.to_i
armstrongNumber num

puts " "
puts 'Display all Armstrong numbers in a range.'
puts 'Insert the last number of the range'
last = gets.chomp.to_i
first = 0
while first <= last
  armstrongNumber first
  first = first + 1
end