Start adding some i18n.

app/controllers/application_controller.rb

@@ -1,3 +1,15 @@
 class ApplicationController < ActionController::Base
   protect_from_forgery
+
+  # Setup the locale based on the domain name used to access the website
+  before_filter :set_locale
+
+  private
+
+  # This sets the locale based on hostname. (see config/initializers/locales.rb)
+  # Can be overridden with locale parameter, i.e. http://localhost:3000/?locale=de
+  def set_locale
+    this_domain_ext = request.host.split('.').last
+    I18n.locale = params[:locale] || DEFAULT_LANGUAGE_BY_DOMAIN[this_domain_ext] || 'en'
+  end
 end

app/views/birthdays/index.html.erb

@@ -8,8 +8,8 @@
 
 <div class="row">
   <div class="twelvecol">
-    <h1>Birthdays</h1>
-    <h2>for the next 7 days</h2>
+    <h1><%= t("birthdays.birthdays") %></h1>
+    <h2><%= t("birthdays.for_next_days") %></h2>
   </div>
 </div>
 

config/initializers/locales.rb

@@ -0,0 +1,9 @@
+
+# Build map of domain extensions and their corresponding language.
+# array contains: domain extension, locale
+#
+DEFAULT_LANGUAGE_BY_DOMAIN = {
+  "com" => "en",
+  "net" => "en",
+  "de" => "de"
+}

config/locales/de.yml

@@ -0,0 +1,4 @@
+de:
+  birthdays:
+    birthdays: "Geburtstage"
+    for_next_days: "für die nächsten 7 Tage"

config/locales/en.yml

@@ -2,4 +2,6 @@
 # See http://github.com/svenfuchs/rails-i18n/tree/master/rails%2Flocale for starting points.
 
 en:
-  hello: "Hello world"
+  birthdays:
+    birthdays: "Birthdays"
+    for_next_days: "for the next 7 days"