Ubiquo i18n

The ubiquo_i18n plugin provides an easy yet powerful way to resolve the common issue that i18n represents to an application.

This plugin is not about the ubiquo interface, which also comes with out of the box i18n capabilites (using the Rails i18n system). This is about translating data from models.

It tries to be simple to use, but also is filled with a lot of useful features, among which:

This guide will walk you through ubiquo_i18n internals and show you how to create a ubiquo_i18n-ized model.

1 Creating translatable models

In this example we will create an Article model, which will have some translatable attributes and relations.

1.1 Scaffolding

If you are going to start a fresh new model, the easiest and quickiest way to create a translatable model is using the ubiquo_scaffold

$ script/generate ubiquo_scaffold Article title:string description:string --translatable title,description

If the above is new for you, see the Ubiquo Scaffold guide

This will make the necessary changes in the model, migration, controller and views to create an Article model with translatable title and description.

You can also use the ubiquo_model scaffold if you only need the model itself.

1.2 Manual creation

If you don’t want to use scaffolding, e.g. because the model file that you want to make translatable already exists, these are the changes that you’ll need to do:

1.2.1 Migrations

This is how the migration to create a table of a translated model looks like

create_table :articles, :translatable => true do |t| t.string :title t.string :description ... end

As you can see, the only special thing here is that a translatable option is added, and will result in adding a locale and content_id fields to the articles table. The rest of the attributes are created as usual.

If you want to add the translatable fields manually and not using this :translatable option, note that the content_id field is implemented as a sequence field, not simply an integer.

If the table already exists, you can use change_table:

change_table(:articles, :translatable => true, :locale => 'en') {}

This method will create the needed fields and initialize them for existing instances. The :locale parameter indicates the locale that will be assigned to any existing records. If you don’t specify any locale, Locale.default will be used

1.2.2 Models

As you could see in the above section, in ubiquo_i18n every translated instance is a full instance by itself, with the locale attribute indicating the language the instance is in, and the content_id field to allow relating which instances are translations of which others.

On models, we can indicate which fields can be translated by using

class Article < ActiveRecord::Base translatable :title, :description

The created model file has the title and descriptions fields defined as translatable, but since we actually have one full table row per instance, which attributes are shared and which ones are translatable can be defined dynamically without affecting the db, so this list can be changed from the model at any moment without creating a new migration.

1.3 Using translatable models

So now that we have the Article model, it’s time to use it.

Article.create(:title => 'title', :description => 'desc', :locale => 'en')

This is an old-school create, that simply has an extra argument, the locale this article is written in. This locale argument is not required, it’s only needed if we want to explicitly set which locale this instance will be in. In Ubiquo, the Locale.current method returns the locale in which we are currently working, the one that can be set using the selector:

Locale selector

Locale.current is not the same as I18n.locale. The first is about content, the latter about interface. Their value is independently set and can be different. See Ubiquo Core guide for information on how to configure the locales of your project.

The previous call to Article.create will fill the content_id field with a new, unique value, since this is a new Article, not a translation of an existing one. If the latter is what we are looking for, we would use:


This will return a new, unsaved article which shares the same content_id with Article.first. But the content_id is not the only thing that is shared, by default it will fill all the attributes with the values of Article.first.

If you don’t want to fill the translatable fields with their original value, use:

Article.first.translate('ca', :copy_all => false)

In either case, if you now do the following:

Article.first.update_attribute(:title => 'new_title')

It will work as expected, just updating the title in Article.first. Had :title been not defined as a translatable attribute, ‘new_title’ would have been set as the title in all the Article instances sharing the same content_id.

1.4 locale() method

The locale() method is one of the most useful and powerful in ubiquo_i18n. You can think of it as a named scope that accepts a list of locales, and will return the instances matching the given locales taking the order as the preference. This is easily seen with examples:

Article.locale('en') # returns all articles in English Article.locale('en', 'ca').count # returns the count of all the articles that have an English and/or a Catalan version Article.locale('en', :ALL) # returns all the articles in English if they have an English version, otherwise in any language Article.first.in_locale('en', 'es', 'ca') # If an article is in English it is returned, if not, the Spanish version is added, and if neither 'en' nor 'es' locale is present for each different content_id, the Catalan is used. If even this is not found, that content_id will not have any language version returned.

The in_locale() method is the equivalent to the locale() method to be used if we start a locale search from an instance.

1.5 The “any” locale

There is a special value for the locale field: “any”. When an instance has this locale, it means that it is in all the locales at the same time, so a search by any value will succeed:

Article.locale('en') # returns all articles in English (including the ones with locale "any")

1.6 Comparing locales

If you want to compare the locale of an instance to a given value, you should use the special in_locale? method, since it will handle correctly the “any” locale:

@article.locale = 'any' @article.in_locale?('en') # true @article.locale == 'en' # false

If you need to handle this special case, you can also use in_locale? with the :skip_any option:

@article.locale = 'any' @article.in_locale?('en') # true @article.in_locale?('en', :skip_any => true) # false

1.7 Filtering elements by locale in listings

There is a builtin “locale” filter in this plugin to allow you to filter by locale in your scaffolds.

An example of code:

../app/helpers/ubiquo/books_helper.rb ... def book_filters filters_for 'Book' do |f| f.locale end end ...

2 Shared relations

Ubiquo_i18n provides a mechanism to allow nearly transparent shared relations between different translations of the same content. Let’s say that the Article has a relation to a Photo model:

class Article translatable :title, :description has_many :photos

In turn, Photo is also translatable

class Photo translatable :caption

If you want every translation of the article to be related to the same photos, but each pointing to the photo with the correct caption for the article, simply change the has_many declaration to include a :translation_shared option

has_many :photos, :translation_shared => true

The actual retrieved :photos will depend on the Locale.current value:

article = Article.last Locale.current = 'en' first_english_photo = article.photos.first english_caption = first_english_photo.caption Locale.current = 'ca' first_catalan_photo = article.photos.first catalan_caption = first_catalan_photo.caption

and, on a change in the relation contents, these are tracked and updated for each translation:

article = Article.locale('en').last article.photos = [image1, image2] # create a new translation translated_article = article.translate('ca') # translated_article.photos.size is 2 # original caption is not updated (remains English) Locale.current = 'en' translated_photo = translated_article.photos.first.translate('ca') translated_photo.caption = 'Catalan-only caption' ) translated_photo.save # a new photo is created # prints 2 images [image1 and image2] puts article.photos # prints 2 images (the same images since Locale.current is 'en') puts translated_article.photos # prints 2 images [translated_photo and image 2] Locale.current = 'ca' puts article.photos # same as translated_article.photos # prints 'English-only caption' (since it's an attribute of image1, not an association) puts image1.caption # prints 'Catalan-only caption' puts translated_photo.caption # On deletion, original article photos are also deleted translated_article.photos = [] puts article.reload.photos # prints []

Therefore, as you can see, when navigating in associations, independently of the locale the original item is in, the returned associated instances will be the ones in Locale.current if they exist.

This is also integrated to work with ubiquo_media, so if you are using it and want this behaviour you can use

media_attachment :photos, :translation_shared => true

You will need to enable the i18n ubiquo_media connector to be able to use this media_attachment option.

2.1 share_translations_for

The :translation_shared option is ok if you only have one shared relation, but what happens when you have a lot of associations that behave this way?

has_many :books, :translation_shared => true has_many :authors, :translation_shared => true belongs_to :file, :translation_shared => true has_one :biography, :translation_shared => true

Not nice, repetitive and what’s worse, even confusing sometimes, if you have these mixed with some others that are not :translation_shared.

In these cases the share_translations_for method fixes this by allowing to define in a single call all these associations:

share_translations_for :books, :authors, :file, :biography

Using it allows you to define in a single line all the associations that have this special behaviour, so you can have a better tracking of what’s going on in the model. And you can leave the Rails association declarations as usual.

This new method also works seamlessly with media_attachments:

has_many :books, :translation_shared => true media_attachment :images, :translation_shared => true # equivalent to has_many :books media_attachment :images share_translations_for :books, :images

3 Changelog

Lighthouse tickets