Advanced usage

Custom fallback language

By default, fallback is centrally configured with MODELTRANS_FALLBACK. That might not be sufficient, for example if part of the content is created for a single language which is not LANGUAGE_CODE.

In that case, it can be configured per-record using the fallback_language_field argument to TranslationField:

class NewsRoom(models.Model):
    name = models.CharField(max_length=255)
    default_language = models.CharField(max_length=2)

    i18n = TranslationField(fields=("name",), fallback_language_field="default_language")

You can traverse foreign key relations too:

class Article(models.Model):
    content = models.CharField(max_length=255)
    newsroom = models.ForeignKey(NewsRoom)

    i18n = TranslationField(fields=("content",), fallback_language_field="newsroom__default_language")

Note that

• if in this example no newsroom is set yet, the centrally configured fallback is used.
• the original field _always_ contains the language as configured by LANGUAGE_CODE.

With the models above:

nos = NewsRoom.objects.create(name="NOS (en)", default_language="nl", name_nl="NOS (nl)")
article = Article.objects.create(
    newsroom=nos,
    content="US-European ocean monitoring satellite launches into orbit",
    content_nl="VS-Europeese oceaanbewakingssatelliet gelanceerd"
)

with override('de'):
    # If language 'de' is not available, the records default_language will be used.
    print(nos.name)  # 'NOS (nl)'

    #  If language 'de' is not available, the newsroom.default_language will be used.
    print(article.content)  # 'VS-Europeese oceaanbewakingssatelliet gelanceerd'

Inheritance of models with translated fields.

When working with model inheritance, you might want to have different parameters to the i18n-field for the parent and the child model. These parameters can be overridden using the i18n_field_params attribute and on the child class:

from django.db import models
from modeltrans.fields import TranslationField

class ParentModel(models.Model):
    info = models.CharField(max_length=255)

    i18n = TranslationField(fields=("info",), required_languages=("en",))


class ChildModel(ParentModel):
    child_info = models.CharField(max_length=255)

    i18n_field_params = {
        "fields": ("info", "child_info"),
        "required_languages": ("nl",)
    }