Rails friendly id with non-Latin characters

Question

I have a model which I use its friendly id as slug:

extend FriendlyId
friendly_id :slug_candidates, :use => :scoped, :scope => :account

def slug_candidates
  :title_and_sequence
end


def title_and_sequence
  slug = normalize_friendly_id(title)
      :
  # some login to add sequence in case of collision
      :
end

My problem is that when I use non-Latin chars (Arab, Hebrew,...) I get an empty slug. Is there any nice-and-easy solution?

---

UPDATE

Just to make my question clear, I would like to have the same behaviour as WordPress, which means:

+--------------------+----------------------------------------------------+
| Title              | url                                                |
+--------------------+----------------------------------------------------+
| Hello World!!      | /hello-world                                       |
+--------------------+----------------------------------------------------+
| Helló Világ        | /hello-vilag                                       |
+--------------------+----------------------------------------------------+
| שלום עולם          | /%D7%A9%D7%9C%D7%95%D7%9D-%D7%A2%D7%95%D7%9C%D7%9D |
+--------------------+----------------------------------------------------+
| مرحبا              | %D9%85%D8%B1%D8%AD%D8%A8%D8%A7                     |
+--------------------+----------------------------------------------------+

(both Arabic and Hebrew are translated in modern browsers to original and readable characters).

Answer 1

Thanks to @michalszyndel notes and ideas I managed to get the following solution, hope it will be helpful for more people.

First, how to make non-unicode chars in slug:

extend FriendlyId
friendly_id :slug_candidates, :use => :scoped, :scope => :account

def slug_candidates
  :title_and_sequence
end

def title_and_sequence
  # This line switch all special chars to its unicode
  title_unicode = heb_to_unicode(title)

  slug = normalize_friendly_id(title_unicode)
      :
  # some login to add sequence in case of collision
  # and whatever you need from your slug
      :
end

def heb_to_unicode(str)
  heb_chars = 'אבגדהוזחטיכךלמםנןסעפףצץקרשת'
  heb_map = {}
  heb_chars.split("").each {|c| heb_map.merge!({c => URI::encode(c)})}
  # This regex replace all Hebrew letters to their unicode representation
  heb_re = Regexp.new(heb_map.keys.map { |x| Regexp.escape(x) }.join('|'))

  return str.gsub(heb_re, heb_map)
end

I also needed to modify normalize_friendly_id in order to avoid it to get rid of the %.
I simply took the code of parameterize method and added % to the regex:

def normalize_friendly_id(string)
  # replace accented chars with their ascii equivalents
  parameterized_string = I18n.transliterate(string)

  sep = '-'

  # Turn unwanted chars into the separator
  # We permit % in order to allow unicode in slug
  parameterized_string.gsub!(/[^a-zA-Z0-9\-_\%]+/, sep)
  unless sep.nil? || sep.empty?
    re_sep = Regexp.escape(sep)
    # No more than one of the separator in a row.
    parameterized_string.gsub!(/#{re_sep}{2,}/, sep)
    # Remove leading/trailing separator.
    parameterized_string.gsub!(/^#{re_sep}|#{re_sep}$/, '')
  end
  parameterized_string.downcase
end

Now if I save a model with the title שלום its slug is saved as %D7%A9%D7%9C%D7%95%D7%9D.
In order to find the instance using the friendly method I need to do the following:

id = URI::encode(params[:id]).downcase
Page.friendly.find(id)