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TwitterCldr uses Unicode's Common Locale Data Repository (CLDR) to format certain types of text into their localized equivalents. Currently supported types of text include dates, times, currencies, decimals, percentages, and symbols.


gem install twitter_cldr


require 'twitter_cldr'


Get a list of all currently supported locales (these are all supported on

TwitterCldr.supported_locales             # [:ar, :da, :de, :en, :es, ... ]

Determine if a locale is supported by TwitterCLDR:

TwitterCldr.supported_locale?(:es)        # true
TwitterCldr.supported_locale?(:xx)        # false

TwitterCldr patches core Ruby objects like Fixnum and Date to make localization as straightforward as possible.


Note: The CLDR is missing complete number data for:

  • hu (Hungarian)
  • id (Indonesian)
  • msa (Malay)
  • no (Norwegian),
  • zh-tw (Traditional Chinese)

Fixnum, Bignum, and Float objects are supported. Here are some examples:

# default formatting with to_s
1337.localize(:es).to_s                                    # 1.337

# currencies, default USD
1337.localize(:es).to_currency.to_s                        # $1.337,00
1337.localize(:es).to_currency.to_s(:currency => "EUR")    # € 1.337,00
1337.localize(:es).to_currency.to_s(:currency => "Peru")   # S/. 1.337,00

# percentages
1337.localize(:es).to_percent.to_s                         # 1.337%
1337.localize(:es).to_percent.to_s(:precision => 2)        # 1.337,00%

# decimals
1337.localize(:es).to_decimal.to_s(:precision => 3)        # 1.337,000

Note: The :precision option can be used with all these number formatters.

Behind the scenes, these convenience methods are creating instances of LocalizedNumber. You can do the same thing if you're feeling adventurous:

num =, :es)
num.to_currency.to_s  # ...etc

More on Currencies

If you're looking for a list of supported countries and currencies, use the TwitterCldr::Shared::Currencies class:

# all supported countries
TwitterCldr::Shared::Currencies.countries                  # ["Lithuania", "Philippines", ... ]

# all supported currency codes
TwitterCldr::Shared::Currencies.currency_codes             # ["LTL", "PHP" ... ]

# data for a specific country
TwitterCldr::Shared::Currencies.for_country("Canada")      # { :currency => "Dollar", :symbol => "$", :code => "CAD" }

# data for a specific currency code
TwitterCldr::Shared::Currencies.for_code("CAD")            # { :currency => "Dollar", :symbol => "$", :country => "Canada"}

Dates and Times

Date, Time, and DateTime objects are supported:                    # "21:44:57 UTC -0800 lunes 12 de diciembre de 2011"                    # "21:45:42 -08:00 12 de diciembre de 2011"                  # "21:46:09 12/12/2011"                   # "21:47 12/12/11"                      # "lunes 12 de diciembre de 2011"                      # "12 de diciembre de 2011"                    # "12/12/2011"                     # "12/12/11"                        # "21:44:57 UTC -0800"                        # "21:45:42 -08:00"                      # "21:46:09"                       # "21:47"

The CLDR data set only includes 4 specific date formats, full, long, medium, and short, so you'll have to choose amongst them for the one that best fits your needs. Yes, it's limiting, but the 4 formats get the job done most of the time :)

Behind the scenes, these convenience methods are creating instances of LocalizedDate, LocalizedTime, and LocalizedDateTime. You can do the same thing if you're feeling adventurous:

dt =, :es)
dt.to_short_s  # ...etc

Plural Rules

Some languages, like English, have "countable" nouns. You probably know this concept better as "plural" and "singular", i.e. the difference between "strawberry" and "strawberries". Other languages, like Russian, have three plural forms: one (numbers ending in 1), few (numbers ending in 2, 3, or 4), and many (everything else). Still other languages like Japanese don't use countable nouns at all.

TwitterCLDR makes it easy to find the plural rules for any numeric value:

1.localize(:ru).plural_rule                                # :one
2.localize(:ru).plural_rule                                # :few
5.localize(:ru).plural_rule                                # :many

Behind the scenes, these convenience methods use the TwitterCldr::Formatters::Plurals::Rules class. You can do the same thing (and a bit more) if you're feeling adventurous:

# get all rules for the default locale
TwitterCldr::Formatters::Plurals::Rules.all                # [:one, ... ]

# get all rules for a specific locale
TwitterCldr::Formatters::Plurals::Rules.all_for(:es)       # [:one, :other]
TwitterCldr::Formatters::Plurals::Rules.all_for(:ru)       # [:one, :few, :many, :other]

# get the rule for a number in a specific locale
TwitterCldr::Formatters::Plurals::Rules.rule_for(1, :ru)   # :one
TwitterCldr::Formatters::Plurals::Rules.rule_for(2, :ru)   # :few

World Languages

You can use the localize convenience method on language code symbols to get their equivalents in another language:

:es.localize(:es).as_language_code                         # "español"
:ru.localize(:es).as_language_code                         # "ruso"

Behind the scenes, these convenience methods are creating instances of LocalizedSymbol. You can do the same thing if you're feeling adventurous:

ls =, :es)
ls.as_language_code  # "ruso"

In addition to translating language codes, TwitterCLDR provides access to the full set of supported languages via the TwitterCldr::Shared::Languages class:

# get all languages for the default locale
TwitterCldr::Shared::Languages.all                                                  # { ... :"zh-Hant" => "Traditional Chinese", :vi => "Vietnamese" ... }

# get all languages for a specific locale
TwitterCldr::Shared::Languages.all_for(:es)                                         # { ... :"zh-Hant" => "chino tradicional", :vi => "vietnamita" ... }

# get a language by its code for the default locale
TwitterCldr::Shared::Languages.from_code(:'zh-Hant')                                # "Traditional Chinese"

# get a language from its code for a specific locale
TwitterCldr::Shared::Languages.from_code_for_locale(:'zh-Hant', :es)                # "chino tradicional"

# translate a language from one locale to another
# signature: translate_language(lang, source_locale, destination_locale)
TwitterCldr::Shared::Languages.translate_language("chino tradicional", :es, :en)    # "Traditional Chinese"
TwitterCldr::Shared::Languages.translate_language("Traditional Chinese", :en, :es)  # "chino tradicional"

About Twitter-specific Locales

Twitter tries to always use BCP-47 language codes. Data from the CLDR doesn't always match those codes, so TwitterCLDR provides a convert_locale method to convert between the two. All functionality throughout the entire gem defers to convert_locale before retrieving CLDR data. convert_locale supports Twitter-supported BCP-47 language codes as well as CLDR locale codes, so you don't have to guess which one to use. Here are a few examples:

TwitterCldr.convert_locale(:'zh-cn')          # :zh
TwitterCldr.convert_locale(:zh)               # :zh
TwitterCldr.convert_locale(:'zh-tw')          # :'zh-Hant'
TwitterCldr.convert_locale(:'zh-Hant')        # :'zh-Hant'

TwitterCldr.convert_locale(:msa)              # :ms
TwitterCldr.convert_locale(:ms)               # :ms

There are a few functions in TwitterCLDR that don't require a locale code, and instead use the default locale by calling TwitterCldr.get_locale. The get_locale function defers to FastGettext.locale when the FastGettext library is available, and falls back on :en (English) when it's not. (Twitter uses the FastGettext gem to retrieve translations efficiently in Ruby).

TwitterCldr.get_locale    # will return :en

require 'fast_gettext'
FastGettext.locale = "ru"

TwitterCldr.get_locale    # will return :ru


No external requirements.

Running Tests

bundle exec rake should do the trick. Tests are written in RSpec using RR as the mocking framework.




Copyright 2012 Twitter, Inc.

Licensed under the Apache License, Version 2.0:

Future Plans

  • Add Javascript support
  • Implement algorithms for Unicode normalization, collation, and capitalization
  • Patch Ruby 1.8 strings to provide better Unicode support (probably using pack and unpack).