EfficientTranslations

EfficientTranslations is a translation library for ActiveRecord models in Rails 2

I wrote EfficientTranslations because I'm working on several legacy rails apps with performance problems and I cannot migrate to Rails 3.

EfficientTranslations is inspired to both Globalize2 (for models architecture: translations are stored in a separated table) and Puret (for cache mechanics).

Requirements

• ActiveSupport 2.3.x
• ActiveRecord 2.3.x

Architecture

The idea is always the same. One table for model records, another table for model translation records. This architecture works well if app languages could change in the future and you don't want to add a column each time a new language is added, or if you have a large number of translations to manage.

EfficientTranslations is designed to reduce the number of queries done to get model+translations and the amount of data retrieved.

I don't think it's a perfect solution, indeed I think it's far to be a perfect solution, but it's a step forward.

Translate a Model

To explain the gem usage we'll use the following use case:

We need a Product model with two localizable fields:
- name (string)
- another_field (integer)

Migrations

You can create the translation table using the helper create_translation_table. The following:

create_table :products do |t|
  t.timestamps
end
create_translation_table :products, :name => :string, :another_field => :integer

is equivalent to:

create_table :products do |t|
  t.timestamps
end
create_table :product_translations do |t|
  t.references :products, :null => false
  t.string     :locale  , :null => false
  t.string     :name
  t.integer    :another_field
end

Models

Now we have to modify our Product model as the following:

class Prouct < ActiveRecord::Base
  translates :name, :another_field
end

Done! You have the EfficientTranslations power in your hands :-)

Usage

Manage Translations

product = Product.new
I18n.default_locale = :en
I18n.locale = :en

product.name_translation :en # => nil
# .name is a wrapper to .name_translation I18n.locale
product.name # => nil
product.set_name_translation :en, 'Efficient Translations'
# no sql query is executed. When possible, a local collection is used
product.name # => 'Efficient Translations'

I18n.locale = :it
# when the current locale is not found, the default locale will be used
product.name # => 'Efficient Translations'
# if you don't want the default locale fallback
product.name! # => nil
product.name_translation! :it # => nil

# .name= is a wrapper to #set_name_translation I18n.locale
product.name = 'Traduzioni Efficienti'
product.name # => 'Traduzioni Efficienti'

product.name_translations # => { :en => 'Efficient Translations', :it => 'Traduzioni Efficienti' }

# translations are saved in the db
product.save!

# Create a product using nested attributes
Product.create! :translations_attributes => [{:locale => I18n.locale.to_s, :name => 'Another'}]
Product.last.name # => 'Another'

Validators

The validator validates_presence_of_default_locale is provided to prevent a model to be saved without a translation for the default locale. Eg:

class Product < ActiveRecord::Base
  translates :name, :another_field
  validates_presence_of_default_locale
end

Named Scopes and Performances Overview

Three named scopes are defined:

with_translations:

# Fetch products with all translations
Product.with_translations

This will include all the translations record. So in the case you have a product with translations for :en and :it.

p = Product.with_translations.first
p.name # No sql is executed
p.name_translation :it # No sql is executed
p.name_translation :fr # No sql is executed

with_current_translations:

# Fetch products with translations for I18n.locale or I18n.default_locale
Product.with_current_translation

This scope will fetch only the translations you usually need when you fetch your models. It's not perfect. Observe the following code to understand why:

Product.create! :translation_attributes => [
  { :locale => :en, :name => 'Product1'  },
  { :locale => :it, :name => 'Prodotto1' }
]
Product.create! :translation_attributes => [
  { :locale => :it, :name => 'Prodotto2' }
]
I18n.locale = :en

# The second product is not included in the result because it doesn't have the I18n.locale or I18n.default_locale translation
# To prevent this you can use validates_presence_of_default_locale
Product.with_current_translation.size # => 1

p = Product.with_current_translation.first
p.name # => 'Product1'; No qury is executed because we used the named scope
# translations collection doesn't contain the 'it' value, so all calls to 'it' translations will return
# the I18n.default_locale value
p.name_translation :it # => 'Product2'

# To fetch the 'it' value you have to do the following:
p.translations true # reload all translations
p.name_translation :it # => 'Prodotto1'

with_translation_for

This scope behaves like with_current_translation but it will use, in order, a locale of your choice or I18n.default_locale to fetch the translations