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<h2>Chapters</h2>
<ol>
<li>
<a href="#_how_i18n_in_ruby_on_rails_works">How I18n in Ruby on Rails works</a>
<ul>
<li><a href="#_the_overall_architecture_of_the_library">The overall architecture of the library</a></li>
<li><a href="#_the_public_i18n_api">The public I18n API</a></li>
</ul>
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<a href="#_setup_the_rails_application_for_internationalization">Setup the Rails application for internationalization</a>
<ul>
<li><a href="#_configure_the_i18n_module">Configure the I18n module</a></li>
<li><a href="#_optional_custom_i18n_configuration_setup">Optional: custom I18n configuration setup</a></li>
<li><a href="#_setting_and_passing_the_locale">Setting and passing the locale</a></li>
</ul>
</li>
<li>
<a href="#_internationalize_your_application">Internationalize your application</a>
<ul>
<li><a href="#_adding_translations">Adding Translations</a></li>
<li><a href="#_adding_date_time_formats">Adding Date/Time formats</a></li>
</ul>
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<li>
<a href="#_overview_of_the_i18n_api_features">Overview of the I18n API features</a>
<ul>
<li><a href="#_looking_up_translations">Looking up translations</a></li>
<li><a href="#_interpolation">Interpolation</a></li>
<li><a href="#_pluralization">Pluralization</a></li>
<li><a href="#_setting_and_passing_a_locale">Setting and passing a locale</a></li>
</ul>
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<li>
<a href="#_how_to_store_your_custom_translations">How to store your custom translations</a>
<ul>
<li><a href="#_translations_for_activerecord_models">Translations for ActiveRecord models</a></li>
<li><a href="#_other_translations_and_localizations">Other translations and localizations</a></li>
</ul>
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<a href="#_customize_your_i18n_setup">Customize your I18n setup</a>
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<li><a href="#_using_different_backends">Using different backends</a></li>
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<div id="content">
<h1>The Rails Internationalization (I18n) API</h1>
<div id="preamble">
<div class="sectionbody">
<div class="paragraph"><p>The Ruby I18n (shorthand for <em>internationalization</em>) gem which is shipped with Ruby on Rails (starting from Rails 2.2) provides an easy-to-use and extensible framework for translating your application to a single custom language other than English or providing multi-language support in your application.</p></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<img src="./images/icons/note.png" alt="Note" />
</td>
<td class="content">The Ruby I18n framework provides you with all neccessary means for internationalization/localization of your Rails application. You may, however, use any of various plugins and extensions available. See Rails <a href="http://rails-i18n.org/wiki">I18n Wiki</a> for more information.</td>
</tr></table>
</div>
</div>
</div>
<h2 id="_how_i18n_in_ruby_on_rails_works">1. How I18n in Ruby on Rails works</h2>
<div class="sectionbody">
<div class="paragraph"><p>Internationalization is a complex problem. Natural languages differ in so many ways (eg. in pluralization rules) that it is hard to provide tools for solving all problems at once. For that reason the Rails I18n API focuses on:</p></div>
<div class="ulist"><ul>
<li>
<p>
providing support for English and similar languages out of the box
</p>
</li>
<li>
<p>
making it easy to customize and extend everything for other languages
</p>
</li>
</ul></div>
<div class="paragraph"><p>As part of this solution, <strong>every static string in the Rails framework</strong> — eg. ActiveRecord validation messages, time and date formats — <strong>has been internationalized</strong>, so <em>localization</em> of a Rails application means "over-riding" these defaults.</p></div>
<h3 id="_the_overall_architecture_of_the_library">1.1. The overall architecture of the library</h3>
<div class="paragraph"><p>Thus, the Ruby I18n gem is split into two parts:</p></div>
<div class="ulist"><ul>
<li>
<p>
The public API of the i18n framework — a Ruby module with public methods and definitions how the library works
</p>
</li>
<li>
<p>
A default backend (which is intentionally named <em>Simple</em> backend) that implements these methods
</p>
</li>
</ul></div>
<div class="paragraph"><p>As a user you should always only access the public methods on the I18n module, but it is useful to know about the capabilities of the backend.</p></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<img src="./images/icons/note.png" alt="Note" />
</td>
<td class="content">It is possible (or even desirable) to swap the shipped Simple backend with a more powerful one, which would store translation data in a relational database, GetText dictionary, or similar. See section <a href="#_using_different_backends">Using different backends</a> below.</td>
</tr></table>
</div>
<h3 id="_the_public_i18n_api">1.2. The public I18n API</h3>
<div class="paragraph"><p>The most important methods of the I18n API are:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
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<pre><tt>translate <span style="font-style: italic"><span style="color: #9A1900"># Lookup text translations</span></span>
localize <span style="font-style: italic"><span style="color: #9A1900"># Localize Date and Time objects to local formats</span></span></tt></pre></div></div>
<div class="paragraph"><p>These have the aliases #t and #l so you can use them like this:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
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<pre><tt>I18n<span style="color: #990000">.</span>t <span style="color: #FF0000">'store.title'</span>
I18n<span style="color: #990000">.</span>l Time<span style="color: #990000">.</span>now</tt></pre></div></div>
<div class="paragraph"><p>There are also attribute readers and writers for the following attributes:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
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<pre><tt>load_path <span style="font-style: italic"><span style="color: #9A1900"># Announce your custom translation files</span></span>
locale <span style="font-style: italic"><span style="color: #9A1900"># Get and set the current locale</span></span>
default_locale <span style="font-style: italic"><span style="color: #9A1900"># Get and set the default locale</span></span>
exception_handler <span style="font-style: italic"><span style="color: #9A1900"># Use a different exception_handler</span></span>
backend <span style="font-style: italic"><span style="color: #9A1900"># Use a different backend</span></span></tt></pre></div></div>
<div class="paragraph"><p>So, let’s internationalize a simple Rails application from the ground up in the next chapters!</p></div>
</div>
<h2 id="_setup_the_rails_application_for_internationalization">2. Setup the Rails application for internationalization</h2>
<div class="sectionbody">
<div class="paragraph"><p>There are just a few, simple steps to get up and running with I18n support for your application.</p></div>
<h3 id="_configure_the_i18n_module">2.1. Configure the I18n module</h3>
<div class="paragraph"><p>Following the <em>convention over configuration</em> philosophy, Rails will set-up your application with reasonable defaults. If you need different settings, you can overwrite them easily.</p></div>
<div class="paragraph"><p>Rails adds all <tt>.rb</tt> and <tt>.yml</tt> files from <tt>config/locales</tt> directory to your <strong>translations load path</strong>, automatically.</p></div>
<div class="paragraph"><p>See the default <tt>en.yml</tt> locale in this directory, containing a sample pair of translation strings:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>en<span style="color: #990000">:</span>
hello<span style="color: #990000">:</span> <span style="color: #FF0000">"Hello world"</span></tt></pre></div></div>
<div class="paragraph"><p>This means, that in the <tt>:en</tt> locale, the key <em>hello</em> will map to <em>Hello world</em> string. Every string inside Rails is internationalized in this way, see for instance ActiveRecord validation messages in the <a href="http://github.com/rails/rails/blob/master/activerecord/lib/active_record/locale/en.yml"><tt>activerecord/lib/active_record/locale/en.yml</tt></a> file or time and date formats in the <a href="http://github.com/rails/rails/blob/master/activesupport/lib/active_support/locale/en.yml"><tt>activesupport/lib/active_support/locale/en.yml</tt></a> file. You can use YAML or standard Ruby Hashes to store translations in the default (Simple) backend.</p></div>
<div class="paragraph"><p>The I18n library will use <strong>English</strong> as a <strong>default locale</strong>, ie. if you don’t set a different locale, <tt>:en</tt> will be used for looking up translations.</p></div>
<div class="paragraph"><p>The <strong>translations load path</strong> (<tt>I18n.load_path</tt>) is just a Ruby Array of paths to your translation files that will be loaded automatically and available in your application. You can pick whatever directory and translation file naming scheme makes sense for you.</p></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<img src="./images/icons/note.png" alt="Note" />
</td>
<td class="content">The backend will lazy-load these translations when a translation is looked up for the first time. This makes it possible to just swap the backend with something else even after translations have already been announced.</td>
</tr></table>
</div>
<div class="paragraph"><p>The default <tt>environment.rb</tt> files has instruction how to add locales from another directory and how to set different default locale. Just uncomment and edit the specific lines.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-style: italic"><span style="color: #9A1900"># The internationalization framework can be changed</span></span>
<span style="font-style: italic"><span style="color: #9A1900"># to have another default locale (standard is :en) or more load paths.</span></span>
<span style="font-style: italic"><span style="color: #9A1900"># All files from config/locales/*.rb,yml are added automatically.</span></span>
<span style="font-style: italic"><span style="color: #9A1900"># config.i18n.load_path << Dir[File.join(RAILS_ROOT, 'my', 'locales', '*.{rb,yml}')]</span></span>
<span style="font-style: italic"><span style="color: #9A1900"># config.i18n.default_locale = :de</span></span></tt></pre></div></div>
<h3 id="_optional_custom_i18n_configuration_setup">2.2. Optional: custom I18n configuration setup</h3>
<div class="paragraph"><p>For the sake of completeness, let’s mention that if you do not want to use the <tt>environment.rb</tt> file for some reason, you can always wire up things manually, too.</p></div>
<div class="paragraph"><p>To tell the I18n library where it can find your custom translation files you can specify the load path anywhere in your application - just make sure it gets run before any translations are actually looked up. You might also want to change the default locale. The simplest thing possible is to put the following into an <strong>initializer</strong>:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-style: italic"><span style="color: #9A1900"># in config/initializer/locale.rb</span></span>
<span style="font-style: italic"><span style="color: #9A1900"># tell the I18n library where to find your translations</span></span>
I18n<span style="color: #990000">.</span>load_path <span style="color: #990000"><<</span> Dir<span style="color: #990000">[</span> File<span style="color: #990000">.</span>join<span style="color: #990000">(</span>RAILS_ROOT<span style="color: #990000">,</span> <span style="color: #FF0000">'lib'</span><span style="color: #990000">,</span> <span style="color: #FF0000">'locale'</span><span style="color: #990000">,</span> <span style="color: #FF0000">'*.{rb,yml}'</span><span style="color: #990000">)</span> <span style="color: #990000">]</span>
<span style="font-style: italic"><span style="color: #9A1900"># set default locale to something else then :en</span></span>
I18n<span style="color: #990000">.</span>default_locale <span style="color: #990000">=</span> <span style="color: #990000">:</span>pt</tt></pre></div></div>
<h3 id="_setting_and_passing_the_locale">2.3. Setting and passing the locale</h3>
<div class="paragraph"><p>By default the I18n library will use :en (English) as a I18n.default_locale for looking up translations (if you do not specify a locale for a lookup).</p></div>
<div class="paragraph"><p>If you want to translate your Rails application to a single language other than English you can set I18n.default_locale to your locale. If you want to change the locale on a per-request basis though you can set it in a before_filter on the ApplicationController like this:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>before_filter <span style="color: #990000">:</span>set_locale
<span style="font-weight: bold"><span style="color: #0000FF">def</span></span> set_locale
<span style="font-style: italic"><span style="color: #9A1900"># if this is nil then I18n.default_locale will be used</span></span>
I18n<span style="color: #990000">.</span>locale <span style="color: #990000">=</span> params<span style="color: #990000">[:</span>locale<span style="color: #990000">]</span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
<div class="paragraph"><p>This will already work for URLs where you pass the locale as a query parameter as in example.com?locale=pt (which is what Google also does).</p></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<img src="./images/icons/tip.png" alt="Tip" />
</td>
<td class="content">For other URL designs, see <a href="http://rails-i18n.org/wiki/pages/how-to-encode-the-current-locale-in-the-url">How to encode the current locale in the URL</a>.</td>
</tr></table>
</div>
<div class="paragraph"><p>Now you’ve initialized I18n support for your application and told it which locale should be used. With that in place you’re now ready for the really interesting stuff.</p></div>
</div>
<h2 id="_internationalize_your_application">3. Internationalize your application</h2>
<div class="sectionbody">
<div class="paragraph"><p>The process of "internationalization" usually means to abstract all strings and other locale specific bits out of your application. The process of "localization" means to then provide translations and localized formats for these bits. <a href="#1">[1]</a></p></div>
<div class="paragraph"><p>So, let’s internationalize something. You most probably have something like this in one of your applications:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
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http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-style: italic"><span style="color: #9A1900"># config/routes.rb</span></span>
ActionController<span style="color: #990000">::</span>Routing<span style="color: #990000">::</span>Routes<span style="color: #990000">.</span>draw <span style="font-weight: bold"><span style="color: #0000FF">do</span></span> <span style="color: #990000">|</span>map<span style="color: #990000">|</span>
map<span style="color: #990000">.</span>root <span style="color: #990000">:</span>controller <span style="color: #990000">=></span> <span style="color: #FF0000">'home'</span><span style="color: #990000">,</span> <span style="color: #990000">:</span>action <span style="color: #990000">=></span> <span style="color: #FF0000">'index'</span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
<span style="font-style: italic"><span style="color: #9A1900"># app/controllers/home_controller.rb</span></span>
<span style="font-weight: bold"><span style="color: #0000FF">class</span></span> HomeController <span style="color: #990000"><</span> ApplicationController
<span style="font-weight: bold"><span style="color: #0000FF">def</span></span> index
flash<span style="color: #990000">[:</span>notice<span style="color: #990000">]</span> <span style="color: #990000">=</span> <span style="color: #FF0000">"Hello flash!"</span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
<span style="font-style: italic"><span style="color: #9A1900"># app/views/home/index.html.erb</span></span>
<span style="color: #FF0000"><h1></span>Hello world!<span style="color: #FF0000"></h1></span>
<span style="color: #FF0000"><p><%= flash[:notice] %></p></span></tt></pre></div></div>
<div class="paragraph"><p><span class="image">
<img src="images/i18n/demo_untranslated.png" alt="rails i18n demo untranslated" title="rails i18n demo untranslated" />
</span></p></div>
<h3 id="_adding_translations">3.1. Adding Translations</h3>
<div class="paragraph"><p>Obviously there are two strings that are localized to English. In order to internationalize this code replace these strings with calls to Rails' #t helper with a key that makes sense for the translation:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-style: italic"><span style="color: #9A1900"># app/controllers/home_controller.rb</span></span>
<span style="font-weight: bold"><span style="color: #0000FF">class</span></span> HomeController <span style="color: #990000"><</span> ApplicationController
<span style="font-weight: bold"><span style="color: #0000FF">def</span></span> index
flash<span style="color: #990000">[:</span>notice<span style="color: #990000">]</span> <span style="color: #990000">=</span> t<span style="color: #990000">(:</span>hello_flash<span style="color: #990000">)</span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
<span style="font-style: italic"><span style="color: #9A1900"># app/views/home/index.html.erb</span></span>
<span style="color: #FF0000"><h1><%=t :hello_world %></h1></span>
<span style="color: #FF0000"><p><%= flash[:notice] %></p></span></tt></pre></div></div>
<div class="paragraph"><p>When you now render this view it will show an error message that tells you that the translations for the keys :hello_world and :hello_flash are missing.</p></div>
<div class="paragraph"><p><span class="image">
<img src="images/i18n/demo_translation_missing.png" alt="rails i18n demo translation missing" title="rails i18n demo translation missing" />
</span></p></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<img src="./images/icons/note.png" alt="Note" />
</td>
<td class="content">Rails adds a <tt>t</tt> (<tt>translate</tt>) helper method to your views so that you do not need to spell out <tt>I18n.t</tt> all the time. Additionally this helper will catch missing translations and wrap the resulting error message into a <span class="translation_missing">.</td>
</tr></table>
</div>
<div class="paragraph"><p>So let’s add the missing translations (i.e. do the "localization" part):</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
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<pre><tt><span style="font-style: italic"><span style="color: #9A1900"># config/locale/en.yml</span></span>
en<span style="color: #990000">:</span>
hello_world<span style="color: #990000">:</span> Hello World
hello_flash<span style="color: #990000">:</span> Hello Flash
<span style="font-style: italic"><span style="color: #9A1900"># config/locale/pirate.yml</span></span>
pirate<span style="color: #990000">:</span>
hello_world<span style="color: #990000">:</span> Ahoy World
hello_flash<span style="color: #990000">:</span> Ahoy Flash</tt></pre></div></div>
<div class="paragraph"><p>There you go. Because you haven’t changed the default_locale I18n will use English. Your application now shows:</p></div>
<div class="paragraph"><p><span class="image">
<img src="images/i18n/demo_translated_english.png" alt="rails i18n demo translated to english" title="rails i18n demo translated to english" />
</span></p></div>
<div class="paragraph"><p>And when you change the URL to pass the pirate locale you get:</p></div>
<div class="paragraph"><p><span class="image">
<img src="images/i18n/demo_translated_pirate.png" alt="rails i18n demo translated to pirate" title="rails i18n demo translated to pirate" />
</span></p></div>
<div class="paragraph"><p>NOTE You need to restart the server when you add new locale files.</p></div>
<h3 id="_adding_date_time_formats">3.2. Adding Date/Time formats</h3>
<div class="paragraph"><p>Ok, let’s add a timestamp to the view so we can demo the date/time localization feature as well. To localize the time format you pass the Time object to I18n.l or (preferably) use Rails' #l helper. You can pick a format by passing the :format option, by default the :default format is used.</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
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http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-style: italic"><span style="color: #9A1900"># app/views/home/index.html.erb</span></span>
<span style="color: #FF0000"><h1><%=t :hello_world %></h1></span>
<span style="color: #FF0000"><p><%= flash[:notice] %></span><span style="color: #990000"></</span>p
<span style="color: #FF0000"><p><%= l Time.now, :format =></span> <span style="color: #990000">:</span>short <span style="color: #990000">%></span><span style="color: #FF0000"></p></span></tt></pre></div></div>
<div class="paragraph"><p>And in our pirate translations file let’s add a time format (it’s already there in Rails' defaults for English):</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
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<pre><tt><span style="font-style: italic"><span style="color: #9A1900"># config/locale/pirate.yml</span></span>
pirate<span style="color: #990000">:</span>
time<span style="color: #990000">:</span>
formats<span style="color: #990000">:</span>
short<span style="color: #990000">:</span> <span style="color: #FF0000">"arrrround %H'ish"</span></tt></pre></div></div>
<div class="paragraph"><p>So that would give you:</p></div>
<div class="paragraph"><p><span class="image">
<img src="images/i18n/demo_localized_pirate.png" alt="rails i18n demo localized time to pirate" title="rails i18n demo localized time to pirate" />
</span></p></div>
<div class="paragraph"><p>NOTE Right now you might need to add some more date/time formats in order to make the I18n backend work as expected. See the <a href="http://github.com/svenfuchs/rails-i18n/tree/master/rails/locale">rails-i18n repository</a> for starting points.</p></div>
</div>
<h2 id="_overview_of_the_i18n_api_features">4. Overview of the I18n API features</h2>
<div class="sectionbody">
<div class="paragraph"><p>The following purposes are covered:</p></div>
<div class="ulist"><ul>
<li>
<p>
lookup translations
</p>
</li>
<li>
<p>
interpolate data into translations
</p>
</li>
<li>
<p>
pluralize translations
</p>
</li>
<li>
<p>
localize dates, numbers, currency etc.
</p>
</li>
</ul></div>
<h3 id="_looking_up_translations">4.1. Looking up translations</h3>
<h4 id="_basic_lookup_scopes_and_nested_keys">4.1.1. Basic lookup, scopes and nested keys</h4>
<div class="paragraph"><p>Translations are looked up by keys which can be both Symbols or Strings, so these calls are equivalent:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
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<pre><tt>I18n<span style="color: #990000">.</span>t <span style="color: #990000">:</span>message
I18n<span style="color: #990000">.</span>t <span style="color: #FF0000">'message'</span></tt></pre></div></div>
<div class="paragraph"><p>translate also takes a :scope option which can contain one or many additional keys that will be used to specify a “namespace” or scope for a translation key:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
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<pre><tt>I18n<span style="color: #990000">.</span>t <span style="color: #990000">:</span>invalid<span style="color: #990000">,</span> <span style="color: #990000">:</span>scope <span style="color: #990000">=></span> <span style="color: #990000">[:</span>active_record<span style="color: #990000">,</span> <span style="color: #990000">:</span>error_messages<span style="color: #990000">]</span></tt></pre></div></div>
<div class="paragraph"><p>This looks up the :invalid message in the ActiveRecord error messages.</p></div>
<div class="paragraph"><p>Additionally, both the key and scopes can be specified as dot separated keys as in:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
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<pre><tt>I18n<span style="color: #990000">.</span>translate <span style="color: #990000">:</span><span style="color: #FF0000">"active_record.error_messages.invalid"</span></tt></pre></div></div>
<div class="paragraph"><p>Thus the following calls are equivalent:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
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<pre><tt>I18n<span style="color: #990000">.</span>t <span style="color: #FF0000">'active_record.error_messages.invalid'</span>
I18n<span style="color: #990000">.</span>t <span style="color: #FF0000">'error_messages.invalid'</span><span style="color: #990000">,</span> <span style="color: #990000">:</span>scope <span style="color: #990000">=></span> <span style="color: #990000">:</span>active_record
I18n<span style="color: #990000">.</span>t <span style="color: #990000">:</span>invalid<span style="color: #990000">,</span> <span style="color: #990000">:</span>scope <span style="color: #990000">=></span> <span style="color: #FF0000">'active_record.error_messages'</span>
I18n<span style="color: #990000">.</span>t <span style="color: #990000">:</span>invalid<span style="color: #990000">,</span> <span style="color: #990000">:</span>scope <span style="color: #990000">=></span> <span style="color: #990000">[:</span>active_record<span style="color: #990000">,</span> <span style="color: #990000">:</span>error_messages<span style="color: #990000">]</span></tt></pre></div></div>
<h4 id="_defaults">4.1.2. Defaults</h4>
<div class="paragraph"><p>When a default option is given its value will be returned if the translation is missing:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
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http://www.gnu.org/software/src-highlite -->
<pre><tt>I18n<span style="color: #990000">.</span>t <span style="color: #990000">:</span>missing<span style="color: #990000">,</span> <span style="color: #990000">:</span>default <span style="color: #990000">=></span> <span style="color: #FF0000">'Not here'</span>
<span style="font-style: italic"><span style="color: #9A1900"># => 'Not here'</span></span></tt></pre></div></div>
<div class="paragraph"><p>If the default value is a Symbol it will be used as a key and translated. One can provide multiple values as default. The first one that results in a value will be returned.</p></div>
<div class="paragraph"><p>E.g. the following first tries to translate the key :missing and then the key :also_missing. As both do not yield a result the string "Not here" will be returned:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>I18n<span style="color: #990000">.</span>t <span style="color: #990000">:</span>missing<span style="color: #990000">,</span> <span style="color: #990000">:</span>default <span style="color: #990000">=></span> <span style="color: #990000">[:</span>also_missing<span style="color: #990000">,</span> <span style="color: #FF0000">'Not here'</span><span style="color: #990000">]</span>
<span style="font-style: italic"><span style="color: #9A1900"># => 'Not here'</span></span></tt></pre></div></div>
<h4 id="_bulk_and_namespace_lookup">4.1.3. Bulk and namespace lookup</h4>
<div class="paragraph"><p>To lookup multiple translations at once an array of keys can be passed:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>I18n<span style="color: #990000">.</span>t <span style="color: #990000">[:</span>odd<span style="color: #990000">,</span> <span style="color: #990000">:</span>even<span style="color: #990000">],</span> <span style="color: #990000">:</span>scope <span style="color: #990000">=></span> <span style="color: #FF0000">'active_record.error_messages'</span>
<span style="font-style: italic"><span style="color: #9A1900"># => ["must be odd", "must be even"]</span></span></tt></pre></div></div>
<div class="paragraph"><p>Also, a key can translate to a (potentially nested) hash as grouped translations. E.g. one can receive all ActiveRecord error messages as a Hash with:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
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<pre><tt>I18n<span style="color: #990000">.</span>t <span style="color: #FF0000">'active_record.error_messages'</span>
<span style="font-style: italic"><span style="color: #9A1900"># => { :inclusion => "is not included in the list", :exclusion => ... }</span></span></tt></pre></div></div>
<h3 id="_interpolation">4.2. Interpolation</h3>
<div class="paragraph"><p>In many cases you want to abstract your translations so that variables can be interpolated into the translation. For this reason the I18n API provides an interpolation feature.</p></div>
<div class="paragraph"><p>All options besides :default and :scope that are passed to #translate will be interpolated to the translation:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>I18n<span style="color: #990000">.</span>backend<span style="color: #990000">.</span>store_translations <span style="color: #990000">:</span>en<span style="color: #990000">,</span> <span style="color: #990000">:</span>thanks <span style="color: #990000">=></span> <span style="color: #FF0000">'Thanks {{name}}!'</span>
I18n<span style="color: #990000">.</span>translate <span style="color: #990000">:</span>thanks<span style="color: #990000">,</span> <span style="color: #990000">:</span>name <span style="color: #990000">=></span> <span style="color: #FF0000">'Jeremy'</span>
<span style="font-style: italic"><span style="color: #9A1900"># => 'Thanks Jeremy!'</span></span></tt></pre></div></div>
<div class="paragraph"><p>If a translation uses :default or :scope as a interpolation variable an I18n::ReservedInterpolationKey exception is raised. If a translation expects an interpolation variable but it has not been passed to #translate an I18n::MissingInterpolationArgument exception is raised.</p></div>
<h3 id="_pluralization">4.3. Pluralization</h3>
<div class="paragraph"><p>In English there’s only a singular and a plural form for a given string, e.g. "1 message" and "2 messages". Other languages (<a href="http://www.unicode.org/cldr/data/charts/supplemental/language_plural_rules.html#ar">Arabic</a>, <a href="http://www.unicode.org/cldr/data/charts/supplemental/language_plural_rules.html#ja">Japanese</a>, <a href="http://www.unicode.org/cldr/data/charts/supplemental/language_plural_rules.html#ru">Russian</a> and many more) have different grammars that have additional or less <a href="http://www.unicode.org/cldr/data/charts/supplemental/language_plural_rules.html">plural forms</a>. Thus, the I18n API provides a flexible pluralization feature.</p></div>
<div class="paragraph"><p>The :count interpolation variable has a special role in that it both is interpolated to the translation and used to pick a pluralization from the translations according to the pluralization rules defined by CLDR:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
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http://www.gnu.org/software/src-highlite -->
<pre><tt>I18n<span style="color: #990000">.</span>backend<span style="color: #990000">.</span>store_translations <span style="color: #990000">:</span>en<span style="color: #990000">,</span> <span style="color: #990000">:</span>inbox <span style="color: #990000">=></span> <span style="color: #FF0000">{</span>
<span style="color: #990000">:</span>one <span style="color: #990000">=></span> <span style="color: #FF0000">'1 message'</span><span style="color: #990000">,</span>
<span style="color: #990000">:</span>other <span style="color: #990000">=></span> <span style="color: #FF0000">'{{count}} messages'</span>
<span style="color: #FF0000">}</span>
I18n<span style="color: #990000">.</span>translate <span style="color: #990000">:</span>inbox<span style="color: #990000">,</span> <span style="color: #990000">:</span>count <span style="color: #990000">=></span> <span style="color: #993399">2</span>
<span style="font-style: italic"><span style="color: #9A1900"># => '2 messages'</span></span></tt></pre></div></div>
<div class="paragraph"><p>The algorithm for pluralizations in :en is as simple as:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
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<pre><tt>entry<span style="color: #990000">[</span>count <span style="color: #990000">==</span> <span style="color: #993399">1</span> <span style="color: #990000">?</span> <span style="color: #993399">0</span> <span style="color: #990000">:</span> <span style="color: #993399">1</span><span style="color: #990000">]</span></tt></pre></div></div>
<div class="paragraph"><p>I.e. the translation denoted as :one is regarded as singular, the other is used as plural (including the count being zero).</p></div>
<div class="paragraph"><p>If the lookup for the key does not return an Hash suitable for pluralization an I18n::InvalidPluralizationData exception is raised.</p></div>
<h3 id="_setting_and_passing_a_locale">4.4. Setting and passing a locale</h3>
<div class="paragraph"><p>The locale can be either set pseudo-globally to I18n.locale (which uses Thread.current like, e.g., Time.zone) or can be passed as an option to #translate and #localize.</p></div>
<div class="paragraph"><p>If no locale is passed I18n.locale is used:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>I18n<span style="color: #990000">.</span>locale <span style="color: #990000">=</span> <span style="color: #990000">:</span>de
I18n<span style="color: #990000">.</span>t <span style="color: #990000">:</span>foo
I18n<span style="color: #990000">.</span>l Time<span style="color: #990000">.</span>now</tt></pre></div></div>
<div class="paragraph"><p>Explicitely passing a locale:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>I18n<span style="color: #990000">.</span>t <span style="color: #990000">:</span>foo<span style="color: #990000">,</span> <span style="color: #990000">:</span>locale <span style="color: #990000">=></span> <span style="color: #990000">:</span>de
I18n<span style="color: #990000">.</span>l Time<span style="color: #990000">.</span>now<span style="color: #990000">,</span> <span style="color: #990000">:</span>locale <span style="color: #990000">=></span> <span style="color: #990000">:</span>de</tt></pre></div></div>
<div class="paragraph"><p>I18n.locale defaults to I18n.default_locale which defaults to :en. The default locale can be set like this:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>I18n<span style="color: #990000">.</span>default_locale <span style="color: #990000">=</span> <span style="color: #990000">:</span>de</tt></pre></div></div>
</div>
<h2 id="_how_to_store_your_custom_translations">5. How to store your custom translations</h2>
<div class="sectionbody">
<div class="paragraph"><p>The shipped Simple backend allows you to store translations in both plain Ruby and YAML format. <a href="#2">[2]</a></p></div>
<div class="paragraph"><p>For example a Ruby Hash providing translations can look like this:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
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<pre><tt><span style="color: #FF0000">{</span>
<span style="color: #990000">:</span>pt <span style="color: #990000">=></span> <span style="color: #FF0000">{</span>
<span style="color: #990000">:</span>foo <span style="color: #990000">=></span> <span style="color: #FF0000">{</span>
<span style="color: #990000">:</span>bar <span style="color: #990000">=></span> <span style="color: #FF0000">"baz"</span>
<span style="color: #FF0000">}</span>
<span style="color: #FF0000">}</span>
<span style="color: #FF0000">}</span></tt></pre></div></div>
<div class="paragraph"><p>The equivalent YAML file would look like this:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>pt<span style="color: #990000">:</span>
foo<span style="color: #990000">:</span>
bar<span style="color: #990000">:</span> baz</tt></pre></div></div>
<div class="paragraph"><p>As you see in both cases the toplevel key is the locale. :foo is a namespace key and :bar is the key for the translation "baz".</p></div>
<div class="paragraph"><p>Here is a "real" example from the ActiveSupport en.yml translations YAML file:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>en<span style="color: #990000">:</span>
date<span style="color: #990000">:</span>
formats<span style="color: #990000">:</span>
default<span style="color: #990000">:</span> <span style="color: #FF0000">"%Y-%m-%d"</span>
short<span style="color: #990000">:</span> <span style="color: #FF0000">"%b %d"</span>
long<span style="color: #990000">:</span> <span style="color: #FF0000">"%B %d, %Y"</span></tt></pre></div></div>
<div class="paragraph"><p>So, all of the following equivalent lookups will return the :short date format "%B %d":</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>I18n<span style="color: #990000">.</span>t <span style="color: #FF0000">'date.formats.short'</span>
I18n<span style="color: #990000">.</span>t <span style="color: #FF0000">'formats.short'</span><span style="color: #990000">,</span> <span style="color: #990000">:</span>scope <span style="color: #990000">=></span> <span style="color: #990000">:</span>date
I18n<span style="color: #990000">.</span>t <span style="color: #990000">:</span>short<span style="color: #990000">,</span> <span style="color: #990000">:</span>scope <span style="color: #990000">=></span> <span style="color: #FF0000">'date.formats'</span>
I18n<span style="color: #990000">.</span>t <span style="color: #990000">:</span>short<span style="color: #990000">,</span> <span style="color: #990000">:</span>scope <span style="color: #990000">=></span> <span style="color: #990000">[:</span>date<span style="color: #990000">,</span> <span style="color: #990000">:</span>formats<span style="color: #990000">]</span></tt></pre></div></div>
<div class="paragraph"><p>Generally we recommend using YAML as a format for storing translations. There are cases though where you want to store Ruby lambdas as part of your locale data, e.g. for special date</p></div>
<h3 id="_translations_for_activerecord_models">5.1. Translations for ActiveRecord models</h3>
<div class="paragraph"><p>You can use the methods Model.human_name and Model.human_attribute_name(attribute) to transparently lookup translations for your model and attribute names.</p></div>
<div class="paragraph"><p>For example when you add the following translations:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>en<span style="color: #990000">:</span>
activerecord<span style="color: #990000">:</span>
models<span style="color: #990000">:</span>
user<span style="color: #990000">:</span> Dude
attributes<span style="color: #990000">:</span>
user<span style="color: #990000">:</span>
login<span style="color: #990000">:</span> <span style="color: #FF0000">"Handle"</span>
<span style="font-style: italic"><span style="color: #9A1900"># will translate User attribute "login" as "Handle"</span></span></tt></pre></div></div>
<div class="paragraph"><p>Then User.human_name will return "Dude" and User.human_attribute_name(:login) will return "Handle".</p></div>
<h4 id="_error_message_scopes">5.1.1. Error message scopes</h4>
<div class="paragraph"><p>ActiveRecord validation error messages can also be translated easily. ActiveRecord gives you a couple of namespaces where you can place your message translations in order to provide different messages and translation for certain models, attributes and/or validations. It also transparently takes single table inheritance into account.</p></div>
<div class="paragraph"><p>This gives you quite powerful means to flexibly adjust your messages to your application’s needs.</p></div>
<div class="paragraph"><p>Consider a User model with a validates_presence_of validation for the name attribute like this:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
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<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> User <span style="color: #990000"><</span> ActiveRecord<span style="color: #990000">::</span>Base
validates_presence_of <span style="color: #990000">:</span>name
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
<div class="paragraph"><p>The key for the error message in this case is :blank. ActiveRecord will lookup this key in the namespaces:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>activerecord<span style="color: #990000">.</span>errors<span style="color: #990000">.</span>messages<span style="color: #990000">.</span>models<span style="color: #990000">.[</span>model_name<span style="color: #990000">].</span>attributes<span style="color: #990000">.[</span>attribute_name<span style="color: #990000">]</span>
activerecord<span style="color: #990000">.</span>errors<span style="color: #990000">.</span>messages<span style="color: #990000">.</span>models<span style="color: #990000">.[</span>model_name<span style="color: #990000">]</span>
activerecord<span style="color: #990000">.</span>errors<span style="color: #990000">.</span>messages</tt></pre></div></div>
<div class="paragraph"><p>Thus, in our example it will try the following keys in this order and return the first result:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>activerecord<span style="color: #990000">.</span>errors<span style="color: #990000">.</span>messages<span style="color: #990000">.</span>models<span style="color: #990000">.</span>user<span style="color: #990000">.</span>attributes<span style="color: #990000">.</span>name<span style="color: #990000">.</span>blank
activerecord<span style="color: #990000">.</span>errors<span style="color: #990000">.</span>messages<span style="color: #990000">.</span>models<span style="color: #990000">.</span>user<span style="color: #990000">.</span>blank
activerecord<span style="color: #990000">.</span>errors<span style="color: #990000">.</span>messages<span style="color: #990000">.</span>blank</tt></pre></div></div>
<div class="paragraph"><p>When your models are additionally using inheritance then the messages are looked up for the inherited model class names are looked up.</p></div>
<div class="paragraph"><p>For example, you might have an Admin model inheriting from User:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Admin <span style="color: #990000"><</span> User
validates_presence_of <span style="color: #990000">:</span>name
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span></tt></pre></div></div>
<div class="paragraph"><p>Then ActiveRecord will look for messages in this order:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>activerecord<span style="color: #990000">.</span>errors<span style="color: #990000">.</span>models<span style="color: #990000">.</span>admin<span style="color: #990000">.</span>attributes<span style="color: #990000">.</span>title<span style="color: #990000">.</span>blank
activerecord<span style="color: #990000">.</span>errors<span style="color: #990000">.</span>models<span style="color: #990000">.</span>admin<span style="color: #990000">.</span>blank
activerecord<span style="color: #990000">.</span>errors<span style="color: #990000">.</span>models<span style="color: #990000">.</span>user<span style="color: #990000">.</span>attributes<span style="color: #990000">.</span>title<span style="color: #990000">.</span>blank
activerecord<span style="color: #990000">.</span>errors<span style="color: #990000">.</span>models<span style="color: #990000">.</span>user<span style="color: #990000">.</span>blank
activerecord<span style="color: #990000">.</span>errors<span style="color: #990000">.</span>messages<span style="color: #990000">.</span>blank</tt></pre></div></div>
<div class="paragraph"><p>This way you can provide special translations for various error messages at different points in your models inheritance chain and in the attributes, models or default scopes.</p></div>
<h4 id="_error_message_interpolation">5.1.2. Error message interpolation</h4>
<div class="paragraph"><p>The translated model name and translated attribute name are always available for interpolation.</p></div>
<div class="paragraph"><p></p></div>
<div class="paragraph"><p>count and/or value are available where applicable. Count can be used for pluralization if present:</p></div>
<div class="tableblock">
<table rules="all"
width="100%"
frame="border"
cellspacing="0" cellpadding="4">
<col width="25%" />
<col width="25%" />
<col width="25%" />
<col width="25%" />
<tbody valign="top">
<tr>
<td align="left"><p class="table">validation</p></td>
<td align="left"><p class="table">with option</p></td>
<td align="left"><p class="table">message</p></td>
<td align="left"><p class="table">interpolation</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_confirmation_of</p></td>
<td align="left"><p class="table">-</p></td>
<td align="left"><p class="table">:confirmation</p></td>
<td align="left"><p class="table">-</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_acceptance_of</p></td>
<td align="left"><p class="table">-</p></td>
<td align="left"><p class="table">:accepted</p></td>
<td align="left"><p class="table">-</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_presence_of</p></td>
<td align="left"><p class="table">-</p></td>
<td align="left"><p class="table">:blank</p></td>
<td align="left"><p class="table">-</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_length_of</p></td>
<td align="left"><p class="table">:within, :in</p></td>
<td align="left"><p class="table">:too_short</p></td>
<td align="left"><p class="table">count</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_length_of</p></td>
<td align="left"><p class="table">:within, :in</p></td>
<td align="left"><p class="table">:too_long</p></td>
<td align="left"><p class="table">count</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_length_of</p></td>
<td align="left"><p class="table">:is</p></td>
<td align="left"><p class="table">:wrong_length</p></td>
<td align="left"><p class="table">count</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_length_of</p></td>
<td align="left"><p class="table">:minimum</p></td>
<td align="left"><p class="table">:too_short</p></td>
<td align="left"><p class="table">count</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_length_of</p></td>
<td align="left"><p class="table">:maximum</p></td>
<td align="left"><p class="table">:too_long</p></td>
<td align="left"><p class="table">count</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_uniqueness_of</p></td>
<td align="left"><p class="table">-</p></td>
<td align="left"><p class="table">:taken</p></td>
<td align="left"><p class="table">value</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_format_of</p></td>
<td align="left"><p class="table">-</p></td>
<td align="left"><p class="table">:invalid</p></td>
<td align="left"><p class="table">value</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_inclusion_of</p></td>
<td align="left"><p class="table">-</p></td>
<td align="left"><p class="table">:inclusion</p></td>
<td align="left"><p class="table">value</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_exclusion_of</p></td>
<td align="left"><p class="table">-</p></td>
<td align="left"><p class="table">:exclusion</p></td>
<td align="left"><p class="table">value</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_associated</p></td>
<td align="left"><p class="table">-</p></td>
<td align="left"><p class="table">:invalid</p></td>
<td align="left"><p class="table">value</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_numericality_of</p></td>
<td align="left"><p class="table">-</p></td>
<td align="left"><p class="table">:not_a_number</p></td>
<td align="left"><p class="table">value</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_numericality_of</p></td>
<td align="left"><p class="table">:odd</p></td>
<td align="left"><p class="table">:odd</p></td>
<td align="left"><p class="table">value</p></td>
</tr>
<tr>
<td align="left"><p class="table">validates_numericality_of</p></td>
<td align="left"><p class="table">:even</p></td>
<td align="left"><p class="table">:even</p></td>
<td align="left"><p class="table">value</p></td>
</tr>
</tbody>
</table>
</div>
<h4 id="_translations_for_the_activerecord_error_messages_for_helper">5.1.3. Translations for the ActiveRecord error_messages_for helper</h4>
<div class="paragraph"><p>If you are using the ActiveRecord error_messages_for helper you will want to add translations for it.</p></div>
<div class="paragraph"><p>Rails ships with the following translations:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>en<span style="color: #990000">:</span>
activerecord<span style="color: #990000">:</span>
errors<span style="color: #990000">:</span>
template<span style="color: #990000">:</span>
header<span style="color: #990000">:</span>
one<span style="color: #990000">:</span> <span style="color: #FF0000">"1 error prohibited this {{model}} from being saved"</span>
other<span style="color: #990000">:</span> <span style="color: #FF0000">"{{count}} errors prohibited this {{model}} from being saved"</span>
body<span style="color: #990000">:</span> <span style="color: #FF0000">"There were problems with the following fields:"</span></tt></pre></div></div>
<h3 id="_other_translations_and_localizations">5.2. Other translations and localizations</h3>
<div class="paragraph"><p>Rails uses fixed strings and other localizations, such as format strings and other format information in a couple of helpers.</p></div>
<div class="paragraph"><p>TODO list helpers and available keys</p></div>
</div>
<h2 id="_customize_your_i18n_setup">6. Customize your I18n setup</h2>
<div class="sectionbody">
<h3 id="_using_different_backends">6.1. Using different backends</h3>
<div class="paragraph"><p>For several reasons the shipped Simple backend only does the "simplest thing that ever could work" <em>for Ruby on Rails</em> <a href="#3">[3]</a> ... which means that it is only guaranteed to work for English and, as a side effect, languages that are very similar to English. Also, the simple backend is only capable of reading translations but can not dynamically store them to any format.</p></div>
<div class="paragraph"><p>That does not mean you’re stuck with these limitations though. The Ruby I18n gem makes it very easy to exchange the Simple backend implementation with something else that fits better for your needs. E.g. you could exchange it with Globalize’s Static backend:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>I18n<span style="color: #990000">.</span>backend <span style="color: #990000">=</span> Globalize<span style="color: #990000">::</span>Backend<span style="color: #990000">::</span>Static<span style="color: #990000">.</span>new</tt></pre></div></div>
<h3 id="_using_different_exception_handlers">6.2. Using different exception handlers</h3>
<div class="paragraph"><p>The I18n API defines the following exceptions that will be raised by backends when the corresponding unexpected conditions occur:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>MissingTranslationData <span style="font-style: italic"><span style="color: #9A1900"># no translation was found for the requested key</span></span>
InvalidLocale <span style="font-style: italic"><span style="color: #9A1900"># the locale set to I18n.locale is invalid (e.g. nil)</span></span>
InvalidPluralizationData <span style="font-style: italic"><span style="color: #9A1900"># a count option was passed but the translation data is not suitable for pluralization</span></span>
MissingInterpolationArgument <span style="font-style: italic"><span style="color: #9A1900"># the translation expects an interpolation argument that has not been passed</span></span>
ReservedInterpolationKey <span style="font-style: italic"><span style="color: #9A1900"># the translation contains a reserved interpolation variable name (i.e. one of: scope, default)</span></span>
UnknownFileType <span style="font-style: italic"><span style="color: #9A1900"># the backend does not know how to handle a file type that was added to I18n.load_path</span></span></tt></pre></div></div>
<div class="paragraph"><p>The I18n API will catch all of these exceptions when they were thrown in the backend and pass them to the default_exception_handler method. This method will re-raise all exceptions except for MissingTranslationData exceptions. When a MissingTranslationData exception has been caught it will return the exception’s error message string containing the missing key/scope.</p></div>
<div class="paragraph"><p>The reason for this is that during development you’d usually want your views to still render even though a translation is missing.</p></div>
<div class="paragraph"><p>In other contexts you might want to change this behaviour though. E.g. the default exception handling does not allow to catch missing translations during automated tests easily. For this purpose a different exception handler can be specified. The specified exception handler must be a method on the I18n module:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><span style="font-weight: bold"><span style="color: #0000FF">module</span></span> I18n
<span style="font-weight: bold"><span style="color: #0000FF">def</span></span> just_raise_that_exception<span style="color: #990000">(*</span>args<span style="color: #990000">)</span>
<span style="font-weight: bold"><span style="color: #0000FF">raise</span></span> args<span style="color: #990000">.</span>first
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
<span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
I18n<span style="color: #990000">.</span>exception_handler <span style="color: #990000">=</span> <span style="color: #990000">:</span>just_raise_that_exception</tt></pre></div></div>
<div class="paragraph"><p>This would re-raise all caught exceptions including MissingTranslationData.</p></div>
<div class="paragraph"><p>Another example where the default behaviour is less desirable is the Rails TranslationHelper which provides the method #t (as well as #translate). When a MissingTranslationData exception occurs in this context the helper wraps the message into a span with the css class translation_missing.</p></div>
<div class="paragraph"><p>To do so the helper forces I18n#translate to raise exceptions no matter what exception handler is defined by setting the :raise option:</p></div>
<div class="listingblock">
<div class="content"><!-- Generator: GNU source-highlight 2.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt>I18n<span style="color: #990000">.</span>t <span style="color: #990000">:</span>foo<span style="color: #990000">,</span> <span style="color: #990000">:</span><span style="font-weight: bold"><span style="color: #0000FF">raise</span></span> <span style="color: #990000">=></span> <span style="font-weight: bold"><span style="color: #0000FF">true</span></span> <span style="font-style: italic"><span style="color: #9A1900"># always re-raises exceptions from the backend</span></span></tt></pre></div></div>
</div>
<h2 id="_resources">7. Resources</h2>
<div class="sectionbody">
</div>
<h2 id="_footnotes">8. Footnotes</h2>
<div class="sectionbody">
<div class="paragraph"><p><a id="1"></a>[1] Or, to quote <a href="http://en.wikipedia.org/wiki/Internationalization_and_localization">Wikipedia</a>: <em>"Internationalization is the process of designing a software application so that it can be adapted to various languages and regions without engineering changes. Localization is the process of adapting software for a specific region or language by adding locale-specific components and translating text."</em></p></div>
<div class="paragraph"><p><a id="2"></a>[2] Other backends might allow or require to use other formats, e.g. a GetText backend might allow to read GetText files.</p></div>
<div class="paragraph"><p><a id="3"></a>[3] One of these reasons is that we don’t want to any unnecessary load for applications that do not need any I18n capabilities, so we need to keep the I18n library as simple as possible for English. Another reason is that it is virtually impossible to implement a one-fits-all solution for all problems related to I18n for all existing languages. So a solution that allows us to exchange the entire implementation easily is appropriate anyway. This also makes it much easier to experiment with custom features and extensions.</p></div>
</div>
<h2 id="_changelog">9. Changelog</h2>
<div class="sectionbody">
<div class="paragraph"><p><a href="http://rails.lighthouseapp.com/projects/16213/tickets/23">Lighthouse ticket</a></p></div>
</div>
</div>
</div>
</body>
</html>
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