django-transmeta 0.6.11

Introduction
============

Transmeta is an application for translatable content in Django's models. Each
language is stored and managed automatically in a different column at database
level.

Features
========

* Automatic schema creation with translatable fields.
* Translatable fields integrated into Django's admin interface.
* Command to synchronize database schema to add new translatable fields and new languages.

Using transmeta
===============

Creating translatable models
----------------------------

Look at this model::

class Book(models.Model):
title = models.CharField(max_length=200)
description = models.TextField()
body = models.TextField(default='')
price = models.FloatField()

Suppose you want to make ``description`` and ``body`` translatable. The resulting model after using ``transmeta`` is::


from transmeta import TransMeta

class Book(models.Model):
__metaclass__ = TransMeta

title = models.CharField(max_length=200)
description = models.TextField()
body = models.TextField(default='')
price = models.FloatField()

class Meta:
translate = ('description', 'body', )

Make sure you have set the default and available languages in your ``settings.py``::

LANGUAGE_CODE = 'es'

ugettext = lambda s: s # dummy ugettext function, as django's docs say

LANGUAGES = (
('es', ugettext('Spanish')),
('en', ugettext('English')),
)

Notes:

* It's possible that you want have a default language in your site, but this is not the default language to transmeta. You can set this variable in your settings::

TRANSMETA_DEFAULT_LANGUAGE = 'it'

* The same it's possible with the languages::

TRANSMETA_LANGUAGES = (
('es', ugettext('Spanish')),
('en', ugettext('English')),
('en', ugettext('Italian')),
)

This is the SQL generated with the ``./manage.py sqlall`` command::

BEGIN;
CREATE TABLE "fooapp_book" (
"id" serial NOT NULL PRIMARY KEY,
"title" varchar(200) NOT NULL,
"description_en" text,
"description_es" text NOT NULL,
"body_es" text NOT NULL,
"body_en" text NOT NULL,
"price" double precision NOT NULL
)
;
COMMIT;

Notes:

* ``transmeta`` creates one column for each language. Don't worry about needing new languages in the future, ``transmeta`` solves this problem for you.
* If one field is ``null=False`` and doesn't have a default value, ``transmeta`` will create only one ``NOT NULL`` field, for the default language. Fields for other secondary languages will be nullable. Also, the primary language will be required in the admin app, while the other fields will be optional (with ``blank=True``). This was done so because the normal approach for content translation is first add content in the main language and later have translators translate into other languages.
* You can use ``./manage.py syncdb`` to create database schema.

Playing in the python shell
---------------------------

``transmeta`` creates one field for every available language for every translatable field defined in a model. Field names are suffixed with language short codes, e.g.: ``description_es``, ``description_en``, and so on. In addition it creates a ``field_name`` getter to retrieve the field value in the active language.

Let's play a bit in a python shell to best understand how this works::

>>> from fooapp.models import Book
>>> b = Book.objects.create(description_es=u'mi descripcion', description_en=u'my description')
>>> b.description
u'my description'
>>> from django.utils.translation import activate
>>> activate('es')
>>> b.description
u'mi descripcion'
>>> b.description_en
u'my description'

Adding new languages
--------------------

If you need to add new languages to the existing ones you only need to change your settings.py and ask transmeta to sync the DB again. For example, to add French to our project, you need to add it to LANGUAGES in ``settings.py``::

LANGUAGES = (
('es', ugettext('Spanish')),
('en', ugettext('English')),
('fr', ugettext('French')),
)

And execute a special ``sync_transmeta_db`` command::

$ ./manage.py sync_transmeta_db

This languages can change in "description" field from "fooapp.book" model: fr

SQL to synchronize "fooapp.book" schema:
ALTER TABLE "fooapp_book" ADD COLUMN "description_fr" text

Are you sure that you want to execute the previous SQL: (y/n) [n]: y
Executing SQL... Done

This languages can change in "body" field from "fooapp.book" model: fr

SQL to synchronize "fooapp.book" schema:
ALTER TABLE "fooapp_book" ADD COLUMN "body_fr" text

Are you sure that you want to execute the previous SQL: (y/n) [n]: y
Executing SQL... Done

And done!

Adding new translatable fields
------------------------------

Now imagine that, after several months using this web app (with many books created), you need to make book price translatable (for example because book price depends on currency).

To achieve this, first add ``price`` to the model's translatable fields list::

class Book(models.Model):
...
price = models.FloatField()

class Meta:
translate = ('description', 'body', 'price', )

All that's left now is calling the ``sync_transmeta_db`` command to update the DB schema::

$ ./manage.py sync_transmeta_db

This languages can change in "price" field from "fooapp.book" model: es, en

SQL to synchronize "fooapp.book" schema:
ALTER TABLE "fooapp_book" ADD COLUMN "price_es" double precision
UPDATE "fooapp_book" SET "price_es" = "price"
ALTER TABLE "fooapp_book" ALTER COLUMN "price_es" SET NOT NULL
ALTER TABLE "fooapp_book" ADD COLUMN "price_en" double precision
ALTER TABLE "fooapp_book" DROP COLUMN "price"

Are you sure that you want to execute the previous SQL: (y/n) [n]: y
Executing SQL...Done

What the hell this command does?

``sync_transmeta_db`` command not only creates new database columns for new translatable field... it copy data from old ``price`` field into one of languages, and that is why command ask you for destination language field for actual data. It's very important that the LANGUAGE_CODE and LANGUAGES (or TRANSMETA_DEFAULT_LANGUAGE, TRANSMETA_LANGUAGES) settings have good values.

This command also you can execute, when you want add a language to the site, or you want to change the default language in ``transmeta``. For this last case, you can define a variable in the settings file::

TRANSMETA_VALUE_DEFAULT = '---'


Admin integration
-----------------

``transmeta`` transparently displays all translatable fields into the admin interface. This is easy because models have in fact many fields (one for each language).

Changing form fields in the admin is quite a common task, and ``transmeta`` includes the ``canonical_fieldname`` utility function to apply these changes for all language fields at once. It's better explained with an example::

from transmeta import canonical_fieldname

class BookAdmin(admin.ModelAdmin):
def formfield_for_dbfield(self, db_field, **kwargs):
field = super(BookAdmin, self).formfield_for_dbfield(db_field, **kwargs)
db_fieldname = canonical_fieldname(db_field)
if db_fieldname == 'description':
# this applies to all description_* fields
field.widget = MyCustomWidget()
elif field.name == 'body_es':
# this applies only to body_es field
field.widget = MyCustomWidget()
return field

Authors
************

transmeta was created at Yaco Systems, originally for Turismo Andaluz.

Transmeta authors are:

* Marc Garcia <garcia.marc@gmail.com>
* Manuel Saelices <msaelices@yaco.es>
* Pablo Martin <goinnn@gmail.com>

Change history
**************

0.6.11 (2013-08-20)
-------------------

- Added get_mandatory_fieldname function.

0.6.10 (2013-03-18)
-------------------

- New TRANSMETA_MANDATORY_LANGUAGE setting, to control which field
will be NOT NULL in the models.

0.6.9 (2012-10-24)
------------------

- Support in method get_field_language for field names with underscores

0.6.8 (2012-06-22)
------------------

- Fix a little bug in the command sync_transmeta_db (UnboundLocalError: local variable 'f' referenced before assignment)

0.6.7 (2012-03-20)
------------------

- Change the representation (verbose_name) of the transmeta labels


0.6.6 (2012-02-06)
------------------

- Improvements and usability in the command sync_transmeta_db
- Fix some bugs
- Documentation


0.6.5 (2012-01-13)
------------------

- Improvements and usability in the command sync_transmeta_db
- Works with the last django (the command sync_transmeta_db)
- Works with mysql (the command sync_transmeta_db)


0.6.4 (2011-11-29)
------------------

- Fixes error with inheritance in models.

0.6.3 (2011-11-29)
------------------

- Allow to use a TRANSMETA_LANGUAGES settings.
- Added two options to sync_transmeta_db: -y (assume yes on all) and -d (default language code)


0.6.2 (2011-03-22)
------------------

- works when default locale have spelling variants as es-ES or en-US.


0.6.1 (2011-03-17)
------------------

- get_all_translatable_fields does not returned the correct tuple. Problems with inheritance.

0.6.0 (2011-02-24)
------------------

- Make compatible with Django 1.2 and 1.3 when using ugettext_lazy in models verbose_name, fixing a hidden bug also for Django 1.1


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********