With the previous versions of Rails we have the choice between storing the translations into a YAML file (one per language) and standard Ruby Hashes.

Bringing the ActiveRecord backend to light, the I18n gem allows us now to manage all our translations in a regular database.

The I18n gem (required to run Rails 3) has been released in late December and is providing all you need to store your translations into a database. A neat thing is the I18n::Backend::Base module, which makes it easy to start writing a new backend in no time.

Today we’ll just configure our Rails 3 application to start storing our translations in our ActiveRecord-baked database.

First of all, let’s create a database table that will be used for the translations. Fire up a new migration and fill-in the blanks in self.up with:

create_table :translations do |t|
  t.string :locale
  t.string :key
  t.text   :value
  t.text   :interpolations
  t.boolean :is_proc, :default => false

This table is required by I18n, but its structure obviously evolve for your own needs. You should now also create a model in app/models/translation.rb:

class Translation < ActiveRecord::Base

Now you can migrate (rake db:migrate), open up your config/application.rb file and modify it to make it looks like this:

module YourApplicationName
  class Application < Rails::Application
    I18n.backend = I18n::Backend::ActiveRecord.new

Voilà! To start creating some translations you can open a Rails console and :

Translation.create!(:locale => "en", :key => "activerecord.models.user", :value => "my user")

[Edit: Feb 28th] : Cédric and Nicolas got it right: you’re gonna run into a lot of troubles if you hit the database each and every time you need a translation. A solution to that: caching. How to proceed? Just again your config/application.rb and add:

I18n.backend = I18n::Backend::ActiveRecord.new
I18n::Backend::ActiveRecord.send(:include, I18n::Backend::Cache)
I18n.cache_store = ActiveSupport::Cache.lookup_store(:memory_store) # or whatever store you prefer

Ain’t it great? :)