Verifying if a ruby string contains one or more accents

contains_accent.rb

# encoding: utf-8

class String
  # The extended characters map used by contains_accent. The accented characters
  # are coded here using their numerical equivalent to sidestep encoding issues.
  # These correspond to ISO-8859-1 encoding.
  ACCENTS_MAPPING = {
    'E' => [200,201,202,203],
    'e' => [232,233,234,235],
    'A' => [192,193,194,195,196,197],
    'a' => [224,225,226,227,228,229,230],
    'C' => [199],
    'c' => [231],
    'O' => [210,211,212,213,214,216],
    'o' => [242,243,244,245,246,248],
    'I' => [204,205,206,207],
    'i' => [236,237,238,239],
    'U' => [217,218,219,220],
    'u' => [249,250,251,252],
    'N' => [209],
    'n' => [241],
    'Y' => [221],
    'y' => [253,255],
    'AE' => [306],
    'ae' => [346],
    'OE' => [188],
    'oe' => [189]
  }

  def contains_accent?
    retval = false
    str = String.new(self)
    String::ACCENTS_MAPPING.each do |letter, accents|
      packed = accents.pack('U*')
      rxp = Regexp.new("[#{packed}]", nil)
      retval = true if str.scan(rxp).size > 0
    end
    retval
  end
end