Classes & Modules


Method Alias Description
localize → l
translate → t



Visibility Signature
public available_locales ()
public backend ()
public backend= (backend)
public default_locale ()
public default_locale= (locale)
public exception_handler= (exception_handler)
public load_path ()
public load_path= (load_path)
public locale ()
public locale= (locale)
public localize (object, options = {})
public reload! ()
public translate (key, options = {})
protected default_exception_handler (exception, locale, key, options)
protected normalize_translation_keys (locale, key, scope)

Class Method Detail


Returns an array of locales for which translations are available


Returns the current backend. Defaults to +Backend::Simple+.


Sets the current backend. Used to set a custom backend.


Returns the current default locale. Defaults to :’en‘


Sets the current default locale. Used to set a custom default locale.


Sets the exception handler.


Allow clients to register paths providing translation data sources. The backend defines acceptable sources.

E.g. the provided SimpleBackend accepts a list of paths to translation files which are either named *.rb and contain plain Ruby Hashes or are named *.yml and contain YAML data. So for the SimpleBackend clients may register translation files like this:

  I18n.load_path << 'path/to/locale/en.yml'


Sets the load path instance. Custom implementations are expected to behave like a Ruby Array.


Returns the current locale. Defaults to I18n.default_locale.


Sets the current locale pseudo-globally, i.e. in the Thread.current hash.

localize(object, options = {})

Localizes certain objects, such as dates and numbers to local formatting.


Tells the backend to reload translations. Used in situations like the Rails development environment. Backends can implement whatever strategy is useful.

translate(key, options = {})

Translates, pluralizes and interpolates a given key using a given locale, scope, and default, as well as interpolation values.


Translation data is organized as a nested hash using the upper-level keys as namespaces. E.g., ActionView ships with the translation: :date => {:formats => {:short => "%b %d"}}.

Translations can be looked up at any level of this hash using the key argument and the scope option. E.g., in this example I18n.t :date returns the whole translations hash {:formats => {:short => "%b %d"}}.

Key can be either a single key or a dot-separated key (both Strings and Symbols work). E.g., the short format can be looked up using both:

  I18n.t 'date.formats.short'
  I18n.t :'date.formats.short'

Scope can be either a single key, a dot-separated key or an array of keys or dot-separated keys. Keys and scopes can be combined freely. So these examples will all look up the same short date format:

  I18n.t 'date.formats.short'
  I18n.t 'formats.short', :scope => 'date'
  I18n.t 'short', :scope => 'date.formats'
  I18n.t 'short', :scope => %w(date formats)


Translations can contain interpolation variables which will be replaced by values passed to translate as part of the options hash, with the keys matching the interpolation variable names.

E.g., with a translation :foo => "foo {{bar}}" the option value for the key bar will be interpolated into the translation:

  I18n.t :foo, :bar => 'baz' # => 'foo baz'


Translation data can contain pluralized translations. Pluralized translations are arrays of singluar/plural versions of translations like [‘Foo’, ‘Foos’].

Note that I18n::Backend::Simple only supports an algorithm for English pluralization rules. Other algorithms can be supported by custom backends.

This returns the singular version of a pluralized translation:

  I18n.t :foo, :count => 1 # => 'Foo'

These both return the plural version of a pluralized translation:

  I18n.t :foo, :count => 0 # => 'Foos'
  I18n.t :foo, :count => 2 # => 'Foos'

The :count option can be used both for pluralization and interpolation. E.g., with the translation :foo => [’{{count}} foo’, ’{{count}} foos’], count will be interpolated to the pluralized translation:

  I18n.t :foo, :count => 1 # => '1 foo'


This returns the translation for :foo or default if no translation was found:

  I18n.t :foo, :default => 'default'

This returns the translation for :foo or the translation for :bar if no translation for :foo was found:

  I18n.t :foo, :default => :bar

Returns the translation for :foo or the translation for :bar or default if no translations for :foo and :bar were found.

  I18n.t :foo, :default => [:bar, 'default']


This returns an array with the translations for :foo and :bar.

  I18n.t [:foo, :bar]

Can be used with dot-separated nested keys:

  I18n.t [:'', :'']

Which is the same as using a scope option:

  I18n.t [:foo, :bar], :scope => :baz

default_exception_handler(exception, locale, key, options)

Handles exceptions raised in the backend. All exceptions except for MissingTranslationData exceptions are re-raised. When a MissingTranslationData was caught and the option :raise is not set the handler returns an error message string containing the key/scope.

normalize_translation_keys(locale, key, scope)

Merges the given locale, key and scope into a single array of keys. Splits keys that contain dots into multiple keys. Makes sure all keys are Symbols.