Added locales controller

app/controllers/locales_controller.rb

@@ -0,0 +1,14 @@
+class LocalesController < ApplicationController
+  before_filter :normalize_http_referer
+
+  # PUT /locales/en/change
+  def change
+    I18n.locale = params[:id]
+    redirect_to :back
+  end
+
+  private
+    def normalize_http_referer
+      request.env["HTTP_REFERER"] ||= "/"
+    end
+end

app/helpers/locales_helper.rb

@@ -0,0 +1,2 @@
+module LocalesHelper
+end

config/routes.rb

@@ -1,3 +1,4 @@
 ActionController::Routing::Routes.draw do |map|
-  map.resources :translations, :only => [ :index ], :member => { :save => :post }
+  map.resources :translations, :only => [ :index ], :member => { :save   => :post }
+  map.resources :locales,      :only => [ ],        :member => { :change => :put  }
 end

test/functional/locales_controller_test.rb

@@ -0,0 +1,14 @@
+require File.expand_path(File.dirname(__FILE__) + '/../test_helper')
+
+class LocalesControllerTest < ActionController::TestCase
+  test "routing" do
+    assert_routing({ :method => :put, :path => "/locales/en/change" },
+      :controller => "locales", :action => "change", :id => "en" )
+  end
+
+  test "should change locale" do
+    put :change, :id => "it"
+    assert_redirected_to "/"
+    assert_equal "it", I18n.locale
+  end
+end