Accessing Translated and Translation Fields¶
The modeltranslation app changes the behaviour of the translated fields. To
explain this consider the news example from the Registering Models for Translation chapter
again. The original News
model looked like this:
class News(models.Model):
title = models.CharField(max_length=255)
text = models.TextField()
Now that it is registered with the modeltranslation app the model looks like this - note the additional fields automatically added by the app:
class News(models.Model):
title = models.CharField(max_length=255) # original/translated field
title_de = models.CharField(null=True, blank=True, max_length=255) # default translation field
title_en = models.CharField(null=True, blank=True, max_length=255) # translation field
text = models.TextField() # original/translated field
text_de = models.TextField(null=True, blank=True) # default translation field
text_en = models.TextField(null=True, blank=True) # translation field
The example above assumes that the default language is de
, therefore the
title_de
and text_de
fields are marked as the default translation
fields. If the default language is en
, the title_en
and text_en
fields would be the default translation fields.
Rules for Translated Field Access¶
So now when it comes to setting and getting the value of the original and the translation fields the following rules apply:
Rule 1
Reading the value from the original field returns the value translated to the current language.
Rule 2
Assigning a value to the original field also updates the value in the associated default translation field.
Rule 3
Assigning a value to the default translation field also updates the original field - note that the value of the original field will not be updated until the model instance is saved.
Rule 4
If both fields - the original and the default translation field - are updated at the same time, the default translation field wins.
Examples for Translated Field Access¶
Because the whole point of using the modeltranslation app is translating
dynamic content, the fields marked for translation are somehow special when it
comes to accessing them. The value returned by a translated field is depending
on the current language setting. “Language setting” is referring to the Django
set_language view and the corresponding get_lang
function.
Assuming the current language is de
in the News example from above, the
translated title
field will return the value from the title_de
field:
# Assuming the current language is "de"
n = News.objects.all()[0]
t = n.title # returns german translation
# Assuming the current language is "en"
t = n.title # returns english translation
This feature is implemented using Python descriptors making it happen without
the need to touch the original model classes in any way. The descriptor uses
the django.utils.i18n.get_language
function to determine the current
language.