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from django.core.exceptions import ImproperlyConfigured
from django.conf import settings
from django.db import models
from django.db.models.base import ModelBase
from django.db.models.signals import post_save
from django.utils.translation import get_language
from nani.descriptors import LanguageCodeAttribute, TranslatedAttribute
from nani.manager import TranslationManager, TranslationsModelManager
from nani.utils import SmartGetFieldByName
from types import MethodType
import sys
def create_translations_model(model, related_name, meta, **fields):
Create the translations model for the shared model 'model'.
'related_name' is the related name for the reverse FK from the translations
'meta' is a (optional) dictionary of attributes for the translations model's
inner Meta class.
'fields' is a dictionary of fields to put on the translations model.
Two fields are enforced on the translations model:
language_code: A 15 char, db indexed field.
master: A ForeignKey back to the shared model.
Those two fields are unique together, this get's enforced in the inner Meta
class of the translations table
if not meta:
meta = {}
unique = [('language_code', 'master')]
meta['unique_together'] = list(meta.get('unique_together', [])) + unique
# Create inner Meta class
Meta = type('Meta', (object,), meta)
if not hasattr(Meta, 'db_table'):
Meta.db_table = model._meta.db_table + '%stranslation' % getattr(settings, 'NANI_TABLE_NAME_SEPARATOR', '_')
Meta.app_label = model._meta.app_label
name = '%sTranslation' % model.__name__
attrs = {}
attrs['Meta'] = Meta
attrs['__module__'] = model.__module__
attrs['objects'] = TranslationsModelManager()
attrs['language_code'] = models.CharField(max_length=15, db_index=True)
# null=True is so we can prevent cascade deletion
attrs['master'] = models.ForeignKey(model, related_name=related_name,
editable=False, null=True)
# Create and return the new model
translations_model = ModelBase(name, (BaseTranslationModel,), attrs)
bases = (model.DoesNotExist, translations_model.DoesNotExist,)
DNE = type('DoesNotExist', bases, {})
translations_model.DoesNotExist = DNE
opts = translations_model._meta
opts.shared_model = model
# Register it as a global in the shared model's module.
# This is needed so that Translation model instances, and objects which
# refer to them, can be properly pickled and unpickled. The Django session
# and caching frameworks, in particular, depend on this behaviour.
mod = sys.modules[model.__module__]
setattr(mod, name, translations_model)
return translations_model
class TranslatedFields(object):
Wrapper class to define translated fields on a model.
def __init__(self, meta=None, **fields):
self.fields = fields
self.meta = meta
def contribute_to_class(self, cls, name):
Called from django.db.models.base.ModelBase.__new__
create_translations_model(cls, name, self.meta, **self.fields)
class BaseTranslationModel(models.Model):
Needed for detection of translation models. Due to the way dynamic classes
are created, we cannot put the 'language_code' field on here.
def __init__(self, *args, **kwargs):
super(BaseTranslationModel, self).__init__(*args, **kwargs)
class Meta:
abstract = True
class TranslatableModelBase(ModelBase):
Metaclass for models with translated fields (TranslatableModel)
def __new__(cls, name, bases, attrs):
super_new = super(TranslatableModelBase, cls).__new__
parents = [b for b in bases if isinstance(b, TranslatableModelBase)]
if not parents:
# If this isn't a subclass of TranslatableModel, don't do anything special.
return super_new(cls, name, bases, attrs)
new_model = super_new(cls, name, bases, attrs)
if not isinstance(new_model.objects, TranslationManager):
raise ImproperlyConfigured(
"The default manager on a TranslatableModel must be a "
"TranslationManager instance or an instance of a subclass of "
"TranslationManager, the default manager of %r is not." %
opts = new_model._meta
if opts.abstract:
return new_model
found = False
for relation in new_model.__dict__.keys():
obj = getattr(new_model, relation)
except AttributeError:
if not hasattr(obj, 'related'):
if not hasattr(obj.related, 'model'):
if getattr(obj.related.model._meta, 'shared_model', None) is new_model:
if found:
raise ImproperlyConfigured(
"A TranslatableModel can only define one set of "
"TranslatedFields, %r defines more than one: %r to %r "
"and %r to %r and possibly more" % (new_model, obj,
obj.related.model, found, found.related.model))
found = obj
if not found:
raise ImproperlyConfigured(
"No TranslatedFields found on %r, subclasses of "
"TranslatableModel must define TranslatedFields." % new_model
post_save.connect(new_model.save_translations, sender=new_model, weak=False)
if not isinstance(opts.get_field_by_name, SmartGetFieldByName):
smart_get_field_by_name = SmartGetFieldByName(opts.get_field_by_name)
opts.get_field_by_name = MethodType(smart_get_field_by_name , opts,
return new_model
class NoTranslation(object):
class TranslatableModel(models.Model):
Base model for all models supporting translated fields (via TranslatedFields).
__metaclass__ = TranslatableModelBase
# change the default manager to the translation manager
objects = TranslationManager()
class Meta:
abstract = True
def __init__(self, *args, **kwargs):
tkwargs = {} # translated fields
skwargs = {} # shared fields
if 'master' in kwargs.keys():
raise RuntimeError(
"Cannot init %s class with a 'master' argument" % \
# filter out all the translated fields (including 'master' and 'language_code')
primary_key_names = ('pk',
for key in kwargs.keys():
if key in self._translated_field_names:
if not key in primary_key_names:
# we exclude the pk of the shared model
tkwargs[key] = kwargs.pop(key)
if not tkwargs.keys():
# if there where no translated options, then we assume this is a
# regular init and don't want to do any funky stuff
super(TranslatableModel, self).__init__(*args, **kwargs)
# there was at least one of the translated fields (or a language_code)
# in kwargs. We need to do magic.
# extract all the shared fields (including the pk)
for key in kwargs.keys():
if key in self._shared_field_names:
skwargs[key] = kwargs.pop(key)
# do the regular init minus the translated fields
super(TranslatableModel, self).__init__(*args, **skwargs)
# prepopulate the translations model cache with an translation model
tkwargs['language_code'] = tkwargs.get('language_code', get_language())
tkwargs['master'] = self
translated = self._meta.translations_model(*args, **tkwargs)
setattr(self, self._meta.translations_cache, translated)
def contribute_translations(cls, rel):
Contribute translations options to the inner Meta class and set the
This get's called from TranslatableModelBase.__new__
opts = cls._meta
opts.translations_accessor = rel.get_accessor_name()
opts.translations_model = rel.model
opts.translations_cache = '%s_cache' % rel.get_accessor_name()
trans_opts = opts.translations_model._meta
# Set descriptors
ignore_fields = [
for field in trans_opts.fields:
if in ignore_fields:
if == 'language_code':
attr = LanguageCodeAttribute(opts)
attr = TranslatedAttribute(opts,
setattr(cls,, attr)
def save_translations(cls, instance, **kwargs):
When this instance is saved, also save the (cached) translation
opts = cls._meta
if hasattr(instance, opts.translations_cache):
trans = getattr(instance, opts.translations_cache)
if not trans.master_id:
trans.master = instance
def translate(self, language_code):
Returns an Model instance in the specified language.
Does NOT check if the translation already exists!
Does NOT interact with the database.
This will refresh the translations cache attribute on the instance.
tkwargs = {
'language_code': language_code,
'master': self,
translated = self._meta.translations_model(**tkwargs)
setattr(self, self._meta.translations_cache, translated)
return self
def safe_translation_getter(self, name, default=None):
cache = getattr(self, self._meta.translations_cache, None)
if not cache:
return default
return getattr(cache, name, default)
def lazy_translation_getter(self, name, default=None):
Lazy translation getter that fetches translations from DB in case the instance is currently untranslated and
saves the translation instance in the translation cache
cache = getattr(self, self._meta.translations_cache, NoTranslation)
trans = self._meta.translations_model.objects.filter(
if not cache and cache != NoTranslation and not trans.exists(): # check if there is no translations
return default
elif getattr(cache, name, NoTranslation) == NoTranslation and trans.exists(): # We have translations, but no specific translation cached
trans_in_own_language = trans.filter(language_code=get_language())
if trans_in_own_language.exists():
trans = trans_in_own_language[0]
trans = trans[0]
setattr(self, self._meta.translations_cache, trans)
return getattr(trans, name)
return getattr(cache, name)
def get_available_languages(self):
manager = self._meta.translations_model.objects
return manager.filter(master=self).values_list('language_code', flat=True)
# Internals
def _shared_field_names(self):
if getattr(self, '_shared_field_names_cache', None) is None:
self._shared_field_names_cache = self._meta.get_all_field_names()
return self._shared_field_names_cache
def _translated_field_names(self):
if getattr(self, '_translated_field_names_cache', None) is None:
self._translated_field_names_cache = self._meta.translations_model._meta.get_all_field_names()
return self._translated_field_names_cache
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