L10n - I18n that roarrrs

L10n provides some useful extensions for Rails I18n, including column translations, localization of numeric form fields and JavaScript translation support.

# Gemfile
gem 'l10n'

In your <locale>.yml, make sure to have definitions for

number:
  precision:
    format:
      delimiter: "."

Translated attributes provide an <attr>_t suffix, which maps to the column determined by the current locale. There is no whatsoever "magic" remapping of actual attributes. The <attr>_t accessor is used exclusively for mapping to the column referred to by the current locale.

class Fruit < ActiveRecord::Base
  # columns: name, name_de, name_fr
  
  translates :name
end

apple = Fruit.new(name: 'Apple', name_de: 'Apfel', name_fr: 'Pomme')

I18n.as(:en) { apple.name_t } => "Apple"
I18n.as(:de) { apple.name_t } => "Apfel"
I18n.as(:fr) { apple.name_t } => "Pomme"

apple.name_translations => { en: "Apple", de: "Apfel", fr: "Pomme" }

The <attr>_t and <attr>_translations setters map to the current locale:

pear = Fruit.new
pear.name_translations = { en: 'Pear', de: 'Birne', fr: 'Poire' }

I18n.locale = :fr
pear.name => "Pear"
pear.name_t => "Poire"

I18n.locale = :en
pear.name => "Pear"
pear.name_t => "Pear"
pear.name_t = 'Williams Christ'
pear.name => "Williams Christ"

Translated columns also support validation:

class Fruit < ActiveRecord::Base
  translates :name
  
  # all translation columns for "name" must be present
  validate :name, translation: true
end

Strings and symbols provide a translate method, aliased as t which maps to I18n.t.

# de.yml
de:
  words:
    one: Eins
    two: Zwei
    three: Drei
    four: Vier
    five: Fünf
    
  hello: "Hallo %{name}!"

I18n.locale = :de

'words.one'.t => 'Eins'

'hello'.t(name: 'Otto') => "Hallo Otto!"

Calling to_lfs on Numerics returns the number as a localized formatted string. The format is defined by the current locale and respects the decimal delimiters and separators defined in your <locale>.yml.

I18n.as('de') { 1234.5.to_lfs } => "1.234,50"
I18n.as('en') { 1234.5.to_lfs } => "1,234.50"

This also works with BigDecimals.

Localization converts decimal separators and delimiters between locales without re-formatting strings. to_ls can be called on any object.

I18n.as('de') { 1234.5.to_localized_s } => "1.234,5"
I18n.as('en') { 1234.5.to_localized_s } => "1,234.5"

I18n.as(:de) { Numeric.localize('1,234.50') } => "1.234,50"
I18n.as(:en) { Numeric.localize('1,234.50') } => "1,234.50"

The amount_field form helper automatically formats numbers in the current locale. Numeric columns automatically convert the localized strings into numbers, respecting decimal delimiters and separators.

# in your template
<%= form_for @car do |f| %>
  <%= f.amount_field :price, precision: 2 %>
<% end %>

# in your controller, or elsewhere
# params => { car: { price: "12.000,00" } }

I18n.locale = :de
@car = Car.new(params[:car]).price => 12000

I18n.locale = :en
@car = Car.new(params[:car]).price => 12

The Accept-Language HTTP header will be parsed, and locales will be returned ordered by user preference. This comes in handy when setting the current locale in a before_action.

# in your controller
request.accept_locales => ["en-US", "en", "en-GB"]

Due to the many different options of integrating JavaScript, the l10n.js file is no longer provided as a standard Rails asset. Instead, it can be installed manually using

rake l10n:install:js

Place your JavaScript translations below the javascript key:

# en.yml
en:
  javascript:
    hello: Hello {name}!
    
    apple:
      one: '{count} apple'
      other: '{count} apples'

Import the module:

import I18n from 'l10n';

Render the translations either as JSON via an endpoint, or include them in a script tag:

I18n.t(:javascript).to_json

Depending on the way the module is integrated, the translations can either be set on the I18n object:

import I18n from 'l10n';
window.I18n = I18n;
I18n.translations = { "hello": "Hello {name}!", "apple": { "one": "{count} apple", "other": "{count} apples" } };

I18n.t("hello", { name: "JS" }) => "Hello JS!"
I18n.t("apple", { count: 5 }) => "5 apples"

or you can supply them as an argument to the translate function:

const translations = { "hello": "Hello {name}!", "apple": { "one": "{count} apple", "other": "{count} apples" } };

I18n.t("hello", { "name": "JS"}, translations)  => "Hello JS!"
I18n.t("apple", { count: 5 }, translations) => "5 apples"