Multi-lingual model in Django used for internationalizing content (See related posts)

The approach taken here gives each object (in this case a wiki Page) a language and a translation_of field. These two fields can be added to any model that wants to add content translations.

Pages are created in a default language. To translate a page, you create a new page and set the translation_of field to the page in the default language that you are translating.

A set of helper methods allow you to get the root version of the page (in the default language), all translations of a page, or a specific translation. These are useful for adding translation links.

   1  
   2  LANGUAGE_CHOICES = (
   3      ('en', 'English'),
   4      ('nl', 'Nederlands')
   5  )
   6  
   7  class Page(models.Model):
   8      language = models.CharField(maxlength=2, choices=LANGUAGE_CHOICES)
   9      title = models.CharField(maxlength=60)
  10      path = models.SlugField(prepopulate_from=('title',))
  11      translation_of = models.ForeignKey('self', related_name='translation_set', limit_choices_to = {'language' : settings.DEFAULT_LANGUAGE}, blank=True, null=True, help_text="Select which page this is a translation of. Don't set this for english pages.", validator_list = [local_models.validate_translation_of])
  12      content = models.TextField(blank=True)
  13  
  14      def get_root_translation(self):
  15          """Returns the root translation for this page.
  16          
  17          This page will be in the settings.DEFAULT_LANGUAGE."""
  18          if self.translation_of is None:
  19              return self
  20          else:
  21              return self.translation_of
  22  
  23      def get_translations(self):
  24          """Return all of the translations for this page."""
  25          # If I am the root translation, just return all of my translations.
  26          if self.translation_of is None:
  27              return self.translation_set.all()
  28          else:
  29              # If I am not the root, return the root translations, plus all of its
  30              # translations, minus myself.
  31              return Page.objects.filter(
  32                  models.Q(id=self.translation_of.id) | 
  33                  models.Q(translation_of=self.translation_of.id)).exclude(pk=self.id)
  34                  
  35      def get_translation(self, language):
  36          """Return a specific translation of this page."""
  37          if self.language == language:
  38              return self
  39          # If I am the root translation, search for translations of me in the given language
  40          elif self.translation_of is None:
  41              try:
  42                  return Page.objects.get(translation_of=self.id, language=language)
  43              except Page.DoesNotExist:
  44                  return None
  45          # Find the root page and the specific translation
  46          else:
  47              # If am not the root, find the root page with the given language,
  48              # otherwise find the page that is a translation of me in the given language
  49              return Page.objects.filter(
  50                  models.Q(id=self.translation_of.id) |
  51                  models.Q(translation_of=self.translation_of.id),
  52                  language=language)

In local_models.py there's this validator to check if the translation_of attribute was not set for pages in the default language:

   1  
   2  def validate_translation_of(field_data, all_data):
   3    if field_data is not None and len(str(field_data)) > 0 and all_data['language'] == settings.DEFAULT_LANGUAGE:
   4      raise validators.ValidationError("Do not set the translation for english pages.")