Ruby i18n - internationalization for ruby

INTERNATIONALIZATION FOR RUBY
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RUBY i18n

INTERNATIONALIZATION FOR PLAIN RUBY: THE RUBY i18n GEM
− Ruby i18n allows translation and localization,interpolation of values to translations,
pluralization,customizable transliteration to ASCII, flexible defaults, bulk lookup,lambdas
as translation data, custom key/scope separator, and custom exception handlers.
− The gem is split in two parts:
− Public API
− Default backend
− YAML (.yml) or plain Ruby (.rb) files are used for storing translationsin SimpleStore,still
YAML is the preferred option among Ruby developers.

INTERNATIONALIZATION AND THE YAML RESOURCE FILE FORMAT
KEY FEATURES OF YAML
− Information is stored in key-value pairs delimited with colon ( : )
− Keys can be nested (scoped)
− i18n expects the root key to correspond to the locale of the content
− The “leaf key” has to have a value
− Values can be escaped
− Correct and consistent line indentation is important for preserving the key hierarchy

INTERNATIONALIZATION AND THE YAML RESOURCE FILE FORMAT
KEY FEATURES OF YAML
− Lines starting with a hash tag sign ( # ) preceded with any number of white-space are
ignored by the parser (treated as a comment)
− Place-holder syntax is: %{name}, where “name” can consist of multiple non-white-space
characters
− UTF-8 encoding is usually used for YAML resource files

EXAMPLE YAML FILE

INSTALLATION AND SETUP
1. gem installation
2. Change the directoryto the location
where the sample YAML file was saved
and start the irb (interactive ruby shell).
3. Check the current locale. (By default it
is English)
4. Changing it something else is easy.
gem install i18n
2.0.0p247 :001 > require ‘i18n’
=> true
2.0.0p247 :002 > I18n.locale
=> :en
2.0.0p247 :003 > I18n.locale = :de
=> :de

TRANSALTION LOOKUP
− Lookup one of the phrases from our
YAML file example
− The translation is missing because we
haven’t loaded the file. Load all .yml and
.rb files in the current directory.
− Retry accessing the English translation
with the key ‘world’
2.0.0p247 :004 > I18n.translate :world,
:scope => ‘greetings.hello’
=> “translation missing: en.hello.world”
2.0.0p247 :005 > I18n.load_path =
Dir[‘./*.yml, ‘./*.rb’]
=> [“./en.yml”]
2.0.0p247 :006 > I18n.translate :world,
:scope => ‘greetings.hello’
=> “Hello world!”

TRANSALTION LOOKUP
− A local can also be explicitly passed
− When passing the phrase key, a symbol or
string can be used, and a scope can be an
array or dot-separated. Combinations of
them are valid too.
2.0.0p247 :007 > I18n.translate :world, :scope
=> ‘greetings.hello’, :locale => :en
=> “Hello world!”
I18n.translate ‘greetings.hello.world’
I18n.translate ‘hello.world’, :scope =>
:greetings
I18n.translate ‘hello.world’, :scope =>
‘greetings’
I18n.translate :world, :scope =>
‘greetings.hello’
I18n.translate :world, scope: [:greetings,
:hello]

TRANSALTION LOOKUP
− Translate the key :missing and the key
:also_missing
− Variables can be interpolated to the
translation
− Pass an array of keys to look up multiple
translations at once
− A key can translate to a hash of grouped
translations
2.0.0p247 :008 > I18n.translate :missing,
default: [:also_missing, ‘Not here’]
=> ‘Not here’
2.0.0p247 :009 > I18n.translate :user, :scope
=> [:greetings, :hello], :user => ‘Ela’
=> “Hello Ela!”
2.0.0p247 :010 > I18n.translate [:world,
:friend], :scope => [:greetings, :hello]
=> [“Hello World!”, “Hello Friend!”]
2.0.0p247 :011 > I18n.translate :hello, :scope
=> [:greetings] => {:world=>”Hello World!”,
:user=>”Hello %{user}”, :friend=>”Hello
Friend!”}

PLUARLIZATION OPTION IN i18n FOR RUBY
− The i18n API providesa flexible
pluralization feature adaptingto the
different grammar of languages.
− The :count interpolation isinterpolated to
the translation and used to pick a
pluralization from the translations
2.0.0p247 :012 > I18n.translate :messages,
:scope => :inbox, :count => 1
=> “You have one message in your inbox.”
2.0.0p247 :013 > I18n.translate :messages,
:scope => :inbox, :count => 39
=> “You have 39 messages in your inbox.”

SETTING UP DATE AND TIME LOCALIZATION
− Pass the Time object to I18n.localize to
localize the time format. Pick a format by
passing the :format option
2.0.0p247 :014 > I18n.localize Time.now
=> “Wed, 14 Aug 2013 13:34:49 +0200”
2.0.0p247 :015 > I18n.localize Time.now,
:format => :short
=> “14 Aug 13:34”
⟶ Instead of I18n.localize,a shorter alias can be used: I18n.l.

i18n – THE DEFAULT INTERNATIONALIZATION SOLUTION FOR RUBY ON RAILS
− Ruby adds all .rb and .yml files from the config/locales directory to translations load path
automatically.
− By default, Rials expects that all the resource files are kept in config/locales.
− You can change some settings by overriding the defaults in application.rb
− Organize the resource files in subdirectories
− Set :de as the default locale
− Set :en, :de and :fr as available locales
Config.i18n.load_path +=
Dir[Rails.root.join(‘config/locales/**/*.{rb,ym
l}’]
config.i18n.default_locale = :de
Config.i18n.available_locales = [:en, :de, :fr]

PASSING THE LOCALE AS A QUERY PARAMETER WITHIN THE URL
− Set the locale in before_action in the
ApplicationController
− This requires passing the locale as a URL
query parameter and adding it to all the
links within the application.
− Rails comes with a helper method that
can be overridden
before_action :set_locale
Def set_locale
I18n.locale = params[:locale] ||
I18n.default_locale
end
# app/controllers/application_controller.rb
def default_url_options(options={})
{ :locale => I18n.locale }
end

PASSING THE LOCALE AS A PART OF THE URL PATH
It is cleaner to have the locale information
at the beginning of the path instead of the
end:
http://localhost:3000/sr/ vs http://localhost:
3000/?locale=sr.
You can do so with the “over-riding
default_url_options”strategy. Just set up the
routes with the scoping option.
# config/routes.rb
scope “(:locale)”, locale: /en|sr/ do
resources :books
end

PASSING THE LOCALE AS A DOMAIN NAME OR A SUBDOMAIN
− Setting the locale from the domain name
or subdomain makes the locale very
obvious and search engines like this
approach too.
− Do so by adding a before_action to the
ApplicationController.
before_action :set_locale
def set_locale
#extracting from the domain name
I18n.locale = extract_locale_from_tld || I18n.default_locale
#extracting from subdomain:
#I18n.locale = extract_locale_from_subdomain || I18n.default_locale
end
def extract_locale_from_tld
parsed_locale = request.host.split('.').last
I18n.available_locales.include?(parsed_locale.to_sym) ?
parsed_locale : nil
end
def extract_locale_from_subdomain
parsed_locale = request.subdomains.first
I18n.available_locales.include?(parsed_locale.to_sym) ?
parsed_locale : nil
end

SETTING THE LOCALE FROM CLIENT-SUPPLIED INFORMATION
− Information other than the page URL can
be used to set the appropriate locale for
the current user.
− An example for a trivial implementation of
using an Accept-Language header
I18n.locale = current_user.locale
def set_locale
I18n.locale =
extract_locale_from_accept_language_header
end
private
def extract_locale_from_accept_language_header
request.env['HTTP_ACCEPT_LANGUAGE'].scan(/
^[a-‐z]{2}/).first
end

TRANSLATION LOOKUP AND DATE/TIME LOCALIZATION BY RUBY ON RAILS
Rails adds t (translate) and l (localize) helper
methods to controllers. They will catch
missing translationsand wrap the resulting
error message into a <span>.
#instead of I18n.translate :hello
t :hello
#instead of I18n.localize Time.now
l Time.now

USING SAFE HTML TRANSLATIONS IN RUBY ON RAILS
− Keys with a ‘_html’ suffix and keys named
‘html’ are marked as HTML safe. Use
them without escaping.
#config/locales/en.yml
en:
welcome: <b>welcome!</b>
hello_html: <b>hello!</b>
title:
html: <b>title!</b>
# app/views/home/index.html.erb
<div><%= t(‘welcome’) %></div>
<div><%= raw t(‘welcome’) %></div>
<div><%= t(‘hello_html’) %></div>
<div><%= t(‘title.html’) %></div>

TRANSLATION FOR ACTIVE RECORD MODELS
− Methods Model.model_name.human and
Model.human_attribute_name(attribute)
can be used to transparentlylook up
translationsfor model and attribute
names.
en:
activerecord:
models:
user: Dude
attributes:
user:
login: “Handle”
# will translate User
attribute “login” as “Handle”

ERROR MESSAGE SCOPES
For example,if there is an ActiveRecord
model “User” that has the :presence
validation for :name, the key for the
message would be :blank. ActiveRecord will
look up for this key in several namespaces,
in this order:
activerecord.errors.models.[model_name].attr
ibutes.[attribute_name]
activerecord.errors.models.[model_name]
activerecord.errors.messages
errors.attributes.[attribute_name]
errors.messages

SENATRA AND PADRINO
I18n FOR

i18n FOR SINATRA
Set up Sinatra to use i18n gem for
internationalization
require ‘i18n’
require ’i18n/backend/fallbacks’
configure
I18n::Backend::Simple.send(:include,
I18n::Backend::Fallbacks)
I18n.load_path, Dir
[File.join(settings.root, ‘locales’,
‘*.yml’)]
I18n.backend.load_translations
end

i18n FOR SINATRA
before ‘/:locale/*’ do
I18n.locale = params[:locale]
request.path_info = ‘/’ +
params[:splat ] [0]
end
before do
if (locale =
request.host.split(‘.’)[0]) != ‘www’
I18n.locale = locale
end
end
use Rack::Locale
Passing the locale
− Specific URLs
− Dedicated subdomains

i18n FOR SINATRA
use Rack::Locale
helpers do
def t(*args)
I18n.t(*args)
end
def l(*args)
I18n.l(*args)
end
end
helpers do
def find_template(views, name, engine, &block)
I18n.fallbacks[I18n.locale].each {
|locale|
super(views,
“#{name}.#{locale}”, engine, &block)}
super(views, name, engine, &block)
end
end
Passing the locale
− Browser preference (requires rack-
contrib)

i18n FOR PADRINO
Localization is fully supported in
− padrino-core (date formats, time formats etc.)
− padrino-admin (admin language, orm fields, orm errors, etc.)
− padrino-helpers(currency, percentage, precision,duration,etc.)
Setting up the default locale in config/boot.rb
Padrino.before_load do
I18n.locale = :en
end

BROUGHT TO YOU BY LINGOHUB
ANJA OBERMÜLLER
BUSINESS DEVELOPMENT& MARKETING AT
LINGOHUB
anja.obermueller@lingohub.com
@LingoHub
@anjaobermueller
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