first translation

app/controllers/application_controller.rb

@@ -2,6 +2,8 @@ class ApplicationController < ActionController::Base
   # Prevent CSRF attacks by raising an exception.
   # For APIs, you may want to use :null_session instead.
   protect_from_forgery with: :exception
+  
+  before_action :set_locale
 
   INPUT_TIMEOUT = 2.seconds # We estimate that a user needs more then x seconds to enter some informations
 
@@ -16,4 +18,13 @@ class ApplicationController < ActionController::Base
   def set_form_timestamp
     session[:form_timestamp] = Time.now
   end
+ 
+  def set_locale
+    I18n.locale = params[:locale] || I18n.default_locale
+  end
+  
+  # I18n set default language in url
+  def default_url_options(options = {})
+    options.merge locale: I18n.locale
+  end
 end