Ruby on Rails - set locale through requests in ruby on rails- ruby on rails tutorial - rails guides - rails tutorial - ruby rails

WeSet locale through requests 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 our controllers, or in ApplicationController to have it in all of our 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

The locale param could come from an URL

http://yourapplication.com/products?locale=en

http://yourapplication.com/products?locale=en

Or

http://yourapplication.com/en/products

To achieve the latter, we need to edit our routes, adding a scope:

# config/routes.rb
scope "(:locale)", locale: /en|fr/ do
  resources :products
end

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.

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

If we 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 our change_language actions

Remember that we need to set our application default locale. We can do it by either setting it in config/application.rb:

config.i18n.default_locale = :de

By creating an initializer in the config/initializers folder:

# config/initializers/locale.rb
I18n.default_locale = :it