Question

I have the following code that is working to assign a locale based first on a param, then a previously set cookie and then by requesting the HTTP_ACCEPT_LANGUAGE.

def set_locale
  if params[:locale] 
    I18n.locale = params[:locale]
  elsif cookies[:locale]
    I18n.locale = cookies[:locale]
  else 
    I18n.locale = sanitizeLocale(request.env["HTTP_ACCEPT_LANGUAGE"]) # e.g. "en,es;q=0.8,de-de;q=0.5,en-us;q=0.3"
  end
  cookies[:locale] = I18n.locale
end

def sanitizeLocale(locale)
  @locale, lang_weight = cookies[:locale] || begin
    if accept_lang = request.env["HTTP_ACCEPT_LANGUAGE"] # e.g. "en,es;q=0.8,de-de;q=0.5,en-us;q=0.3"
      accept_lang.to_s.split(',').collect {|l| x,y = l.split(';q='); [x.split('-').first, (y||1).to_f]}.sort_by(&:last).reverse.find {|lang, lang_weight| %w[es en it fr de].include?(lang)}
      # returns ["en", 1.0]
    end
  end || 'en' # default
  return @locale
end

My question is how can I check both the params[:locale] given and cookies[:locale] against the sanitizeLocale. I’m interesting in only get a valid value such as es en it fr de or default to en based on the input.

I been trying to just pass its values to sanitizeLocale similarly I’m doing for HTTP_ACCEPT_LANGUAGE for some reason I can’t understand is not working and is always defaulting to en even when params[:locale] given values are valid like it.

Answer 1

First, we can simplify your Accept-Language parsing a bit:

def acceptable_langs
  extract_langs = lambda do |l|
    x, y = l.split(';q=')
    [x.split('-').first, -(y || 1).to_f] # the -1 makes sort_by nicer
  end
  known_langs = lambda { |lang| %w[es en it fr de].include?(lang.first) }
  quality = :last
  language = :first
  langs = request.env['HTTP_ACCEPT_LANGUAGE'].to_s
                 .split(',')
                 .map(&extract_langs)
                 .select(&known_langs)
                 .sort_by(&quality)
                 .collect(&:language)
  langs + ['en']
end

The to_s will take care of nils and the lambdas and extra variables are just there to clarify the logic. You don’t have to do this, all you really need is a method that returns the language codes that are acceptable to both the user and your software ordered by the user’s preference.

Now back to set_locale. You say that you need the language to match Accept-Langauge (with 'en' as a fallback) regardless of what the URL or cookies have to say. That means that you have to parse Accept-Language no matter what and then check params[:locale] and cookies[:locale] against that list:

def set_locale
  # Figure out what they're asking for with English as the
  # default. Note that `acceptable_langs` always forces English
  # to be in the list.
  asking_for = params[:locale] || cookies[:locale] || 'en'

  # acceptable_langs is always in preference order so we just
  # want the first one that matches our `lang`.
  lang = acceptable_langs.find { |lang| asking_for == lang }

  # Now we have an acceptable language in `lang` (thanks to all
  # the `'en'` fallbacks we sprinkled about).
  I18n.locale = cookies[:locale] = lang
end

You could also add a little “I’ve already done all this work” flag to the cookies so that you could simply trust cookies[:locale] if the flag is set; there’s probably no reason to prematurely optimize set_locale though.