Rails: FastGettext, I18n integration -- simple, threadsafe and fast!
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FastGettext / Rails integration.

Translate via FastGettext, use any other I18n backend as extension/fallback.

Rails does: I18n.t('syntax.with.lots.of.dots') with nested yml files We do: _('Just translate my damn text!') with simple, flat mo/po/yml files or directly from db To use I18n calls add a syntax.with.lots.of.dots translation.

See it working in the example application.



Rails 3

As plugin:
rails plugin install git://github.com/grosser/gettext_i18n_rails.git

# Gemfile
gem 'fast_gettext', '>=0.4.8'
As gem:
# Gemfile
gem 'gettext_i18n_rails'

Add gettext if you want to find translations or build .mo files
Add ruby_parser if you want to find translations inside haml/slim/hamlet files (does not support ruby 1.9 syntax)

# Gemfile
gem 'gettext', '>=1.9.3', :require => false, :group => :development
gem 'ruby_parser', :require => false, :group => :development

Rails 2

As plugin:
script/plugin install git://github.com/grosser/gettext_i18n_rails.git
sudo gem install fast_gettext

# config/environment.rb
config.gem "fast_gettext", :version => '>=0.4.8'
As gem:
gem install gettext_i18n_rails

# config/environment.rb
config.gem 'gettext_i18n_rails'

  require "gettext_i18n_rails/tasks"
rescue LoadError
  puts "gettext_i18n_rails is not installed, you probably should run 'rake gems:install' or 'bundle install'."

If you want to find translations or build .mo files # config/environments/development.rb config.gem "gettext", :version => '>=1.9.3', :lib => false

Locales & initialisation

Copy default locales with dates/sentence-connectors/AR-errors you want from e.g. rails i18n into 'config/locales'

To initialize:

# config/initializers/fast_gettext.rb
FastGettext.add_text_domain 'app', :path => 'locale', :type => :po
FastGettext.default_available_locales = ['en','de'] #all you want to allow
FastGettext.default_text_domain = 'app'

And in your application:

# app/controllers/application_controller.rb
class ApplicationController < ...
  before_filter :set_gettext_locale


Performance is almost the same for all backends since translations are cached after first use.

Option A: .po files

FastGettext.add_text_domain 'app', :path => 'locale', :type => :po
  • use some _('translations')
  • run rake gettext:find, to let GetText find all translations used
  • (optional) run rake gettext:store_model_attributes, to parse the database for columns that can be translated
  • if this is your first translation: cp locale/app.pot locale/de/app.po for every locale you want to use
  • translate messages in 'locale/de/app.po' (leave msgstr blank and msgstr == msgid)

New translations will be marked "fuzzy", search for this and remove it, so that they will be used. Obsolete translations are marked with ~#, they usually can be removed since they are no longer needed

Unfound translations with rake gettext:find

Dynamic translations like _("x"+"u") cannot be fond. You have 4 options:

  • add N_('xu') somewhere else in the code, so the parser sees it
  • add N_('xu') in a totally separate file like locale/unfound_translations.rb, so the parser sees it
  • use the gettext_test_log rails plugin to find all translations that where used while testing
  • add a Logger to a translation Chain, so every unfound translations is logged (example)

Option B: Traditional .po/.mo files

FastGettext.add_text_domain 'app', :path => 'locale'
  • follow Option A
  • run rake gettext:pack to write binary GetText .mo files

Option C: Database

Most scalable method, all translators can work simultaneously and online.

Easiest to use with the translation database Rails engine. Translations can be edited under /translation_keys

FastGettext.add_text_domain 'app', :type => :db, :model => TranslationKey


I18n.locale <==> FastGettext.locale.to_sym
I18n.locale = :de <==> FastGettext.locale = 'de'

Any call to I18n that matches a gettext key will be translated through FastGettext.


Car|Model means Model in namespace Car. You do not have to translate this into english "Model", if you use the namespace-aware translation s_('Car|Model') == 'Model' #when no translation was found

XSS / html_safe

If you trust your translators and all your usages of % on translations:
# config/environment.rb GettextI18nRails.translations_are_html_safe = true

String % vs html_safe is buggy (can be used for XSS on 1.8 and is always non-safe in 1.9)
My recommended fix is: require 'gettext_i18n_rails/string_interpolate_fix'

  • safe stays safe (escape added strings)
  • unsafe stays unsafe (do not escape added strings)

ActiveRecord - error messages

ActiveRecord error messages are translated through Rails::I18n, but model names and model attributes are translated through FastGettext. Therefore a validation error on a BigCar's wheels_size needs _('big car') and _('BigCar|Wheels size') to display localized.

The model/attribute translations can be found through rake gettext:store_model_attributes, (which ignores some commonly untranslated columns like id,type,xxx_count,...).

Error messages can be translated through FastGettext, if the ':message' is a translation-id or the matching Rails I18n key is translated.

####Option A: Define a translation for "I need my rating!" and use it as message. validates_inclusion_of :rating, :in=>1..5, :message=>N_('I need my rating!')

####Option B: validates_inclusion_of :rating, :in=>1..5 Make a translation for the I18n key: activerecord.errors.models.rating.attributes.rating.inclusion

####Option C: Add a translation to each config/locales/*.yml files en: activerecord: errors: models: rating: attributes: rating: inclusion: " -- please choose!" The rails I18n guide can help with Option B and C.


FastGettext supports pluralization n_('Apple','Apples',3) == 'Apples'

Abnormal plurals like e.g. Polish that has 4 different can also be addressed, see FastGettext Readme

Customizing list of translatable files

When you run

rake gettext:find

by default the following files are going to be scanned for translations: {app,lib,config,locale}/**/*.{rb,erb,haml,slim}. If you want to specify a different list, you can redefine files_to_translate in the gettext namespace in a file like lib/tasks/gettext.rake:

namespace :gettext do
  def files_to_translate


Michael Grosser
Hereby placed under public domain, do what you want, just do not hold me accountable...