Ruby On Rails Blog

Setting User’s Locale Based on Domain Name In Rails

June 18th, 2009

In this tutorial I will show how you can quickly set the user’s locale based on the domain name they use to access your website. Let us assume you have your app, and you also own your own domain in several different country TLD’s, let’s say, you have example.com (main site), example.co.uk, example.fr, example.it example.es, and example.de.

When a user visits www.example.de in their browser, it makes sense that your app should default to showing the user the German (.de) translation of the website.

Here’s how to do it.

First of all, you will need a list of what locale translations are available to use at the current time. To do this, we will create a new file in config/initializers/locales.rb. This will automatically be loaded and parsed when your application starts.

config/initializers/locales.rb:

#
# Build map of domain extensions and their corresponding language.
# array contains: domain extension, locale
#
DEFAULT_LANGUAGE_BY_DOMAIN = []
DEFAULT_LANGUAGE_BY_DOMAIN << ["com", "en"]
DEFAULT_LANGUAGE_BY_DOMAIN << ["uk", "en"]
DEFAULT_LANGUAGE_BY_DOMAIN << ["de", "de"]
DEFAULT_LANGUAGE_BY_DOMAIN << ["fr", "fr"]
DEFAULT_LANGUAGE_BY_DOMAIN << ["it", "it"]
DEFAULT_LANGUAGE_BY_DOMAIN << ["es", "es"]

Now add the following to your app/controllers/application_controller.rb:

  # Setup the locale based on the domain name used to access the website
  before_filter :set_locale
  def set_locale
    # Choose default locale of english
    I18n.default_locale = 'en'

    # Extract domain extension
    this_domain_ext = request.host.split('.').last

    # Search for domain extension in possible exts array, then
    # set the language of the domain if a record is found.
    this_domain_lang = DEFAULT_LANGUAGE_BY_DOMAIN.assoc(this_domain_ext)
    if this_domain_lang then
      I18n.locale = this_domain_lang[1]
    end

    # Allow a URL param to override everything else
    if params[:locale] then
      I18n.locale = params[:locale]
    end
  end

And that's it, all done!

When a user lands your website they will automatically have the correct locale selected for them!

This method also allows a nifty trick for the developer to test with. You can access your German translation on your localhost test site by appending the "locale=xx" query parameter to the URL, for example http://localhost:3000/?locale=de. Great for just quickly checking how something looks while developing.

Categories: Rails, User Experience

Tags: before_filter, development, Domain, language, languages, locale, Rails, usability Leave a comment