Ruby on Rails I18n - Internationalization Set locale through requests
Example
In most cases, you may want to set I18n locale. One might want to set the locale for the current session, the current user, or based on a URL parameter This is easily achievable by implementing a before_action in one of your controllers, or in ApplicationController to have it in all of your controllers.
class ApplicationController < ActionController::Base
before_action :set_locale
protected
def set_locale
# Remove inappropriate/unnecessary ones
I18n.locale = params[:locale] || # Request parameter
session[:locale] || # Current session
(current_user.preferred_locale if user_signed_in?) || # Model saved configuration
extract_locale_from_accept_language_header || # Language header - browser config
I18n.default_locale # Set in your config files, english by super-default
end
# Extract language from request header
def extract_locale_from_accept_language_header
if request.env['HTTP_ACCEPT_LANGUAGE']
lg = request.env['HTTP_ACCEPT_LANGUAGE'].scan(/^[a-z]{2}/).first.to_sym
lg.in?([:en, YOUR_AVAILABLE_LANGUAGES]) ? lg : nil
end
end
URL-based
The locale param could come from an URL like this
http://yourapplication.com/products?locale=en
Or
http://yourapplication.com/en/products
To achieve the latter, you need to edit your routes, adding a scope:
# config/routes.rb
scope "(:locale)", locale: /en|fr/ do
resources :products
end
By doing this, visiting http://yourapplication.com/en/products will set your locale to :en. Instead, visiting http://yourapplication.com/fr/products will set it to :fr. Furthermore, you won't get a routing error when missing the :locale param, as visiting http://yourapplication.com/products will load the default I18n locale.
Session-based or persistence-based
This assumes the user can click on a button/language flag to change the language. The action can route to a controller that sets the session to the current language (and eventually persist the changes to a database if the user is connected)
class SetLanguageController < ApplicationController
skip_before_filter :authenticate_user!
after_action :set_preferred_locale
# Generic version to handle a large list of languages
def change_locale
I18n.locale = sanitize_language_param
set_session_and_redirect
end
You have to define sanitize_language_param with your list of available languages, and eventually handle errors in case the language doesn't exist.
If you have very few languages, it may be worth defining them like this instead:
def fr
I18n.locale = :fr
set_session_and_redirect
end
def en
I18n.locale = :en
set_session_and_redirect
end
private
def set_session_and_redirect
session[:locale] = I18n.locale
redirect_to :back
end
def set_preferred_locale
if user_signed_in?
current_user.preferred_locale = I18n.locale.to_s
current_user.save if current_user.changed?
end
end
end
Note: don't forget to add some routes to your change_language actions
Default Locale
Remember that you need to set your application default locale. You can do it by either setting it in config/application.rb:
config.i18n.default_locale = :de
or by creating an initializer in the config/initializers folder:
# config/initializers/locale.rb
I18n.default_locale = :it
