Solution to Caesar Cipher implemented in ruby

caesar_cipher.rb

def alphabet
  Array('a'..'z') | (Array('A'..'Z'))
end

def cs_encrypt(string, key = 0)
  # Rotate switches alphabets based on the passed key
  dictionary = Hash[alphabet.zip(alphabet.rotate(key))]
  
  string.chars.map { |str| dictionary.fetch(str, ' ') }
end

string = cs_encrypt("onCe Upon a tIme there was a little house On the TOP of the hill", 3).join

puts string