Django - Lesson 059. Saving the selected language in user settings

python, language, django, translation

In this article, I would like to show an example of how you can make a link on the site so that the user can switch between languages on the site.

But I will show a more advanced version of this functionality, namely saving the selected language in the user table, as well as redirecting the user to a page with the correct language that was selected by the user, if they are of course authorized. That is, if the user has set the German language for himself, then when going to the site via an English link, the site will automatically redirect the user to the page with the German language.

To do this, we need to add a language code field to the user model, I hope that everyone is already using their user model in Django instead of the default one.
Rewrite the standard Django language setup function, and also add a Middleware that will process the urls requested from the site.

Among other things, this functionality will be useful in order to generate letters with the correct language for registered users.

This article is based on Django 4 and may not be suitable for older versions of Django.

Set up the user model

Let's add the language field to the user model, in which the code of the selected language will be added, by default it will be the language that is the main language for your site.

Файл yourapp/yourauthapp/models.py

# -*- coding: utf-8 -*-
 
from django.conf import settings
from django.contrib.auth.models import AbstractUser
from django.db import models
 
 
 
class Group(DjangoGroup):
    class Meta:
        proxy = True
 
 
class User(AbstractUser):
    language = models.CharField(max_length=10,
                                choices=settings.LANGUAGES,
                                default=settings.LANGUAGE_CODE)

Accordingly, we will create a migration and execute it.

python manage.py makemigrations
python manage.py migrate

Add a view to set the language

Файл yourapp/yourauthapp/views.py

There are two important points here:

• The original function is to use a form and send a POST message. I prefer the link with the language code.
• In case the user is authorized,

# -*- coding: utf-8 -*-
 
from django.conf import settings
from django.http import HttpResponseRedirect, HttpResponse
from django.urls import translate_url
from django.utils.http import url_has_allowed_host_and_scheme
from django.utils.translation import check_for_language
 
 
def set_language(request, lang_code):
 
    next_url = request.POST.get('next', request.GET.get('next'))
    if (
        (next_url or request.accepts('text/html')) and
        not url_has_allowed_host_and_scheme(
            url=next_url,
            allowed_hosts={request.get_host()},
            require_https=request.is_secure(),
        )
    ):
        next_url = request.META.get('HTTP_REFERER')
        if not url_has_allowed_host_and_scheme(
            url=next_url,
            allowed_hosts={request.get_host()},
            require_https=request.is_secure(),
        ):
            next_url = '/'
    response = HttpResponseRedirect(next_url) if next_url else HttpResponse(status=204)
 
    if request.method == 'GET': # Change method from POST to GET, we want use url parameters for this funcionality
 
        if lang_code and check_for_language(lang_code):
            if next_url:
                next_trans = translate_url(next_url, lang_code)
                if next_trans != next_url:
                    response = HttpResponseRedirect(next_trans)
            response.set_cookie(
                settings.LANGUAGE_COOKIE_NAME, lang_code,
                max_age=settings.LANGUAGE_COOKIE_AGE,
                path=settings.LANGUAGE_COOKIE_PATH,
                domain=settings.LANGUAGE_COOKIE_DOMAIN,
                secure=settings.LANGUAGE_COOKIE_SECURE,
                httponly=settings.LANGUAGE_COOKIE_HTTPONLY,
                samesite=settings.LANGUAGE_COOKIE_SAMESITE,
            )
 
            # Important part of code, set language to user, if user is authenticated
            if request.user.is_authenticated:
                request.user.language = lang_code
                request.user.save(update_fields=['language'])
 
    return response

Include set_language in your main urls.py file

Now you need to connect the view so that you can generate links for switching the language in templates.

# -*- coding: utf-8 -*-
 
from django.urls import path
 
from yourauthapp import views
 
 
urlpatterns = [
    path('lang/<str:lang_code>/', views.set_language, name='lang'),
    ...
]

Generation of links in the template

Note that I add ?next={{ request.path }} to the link to get the correct redirect to the original page where the user chose to switch the language.

{% get_available_languages as LANGUAGES %}
{% get_language_info_list for LANGUAGES as languages %}
{% for language in languages %}
    <a href="{% url 'lang' language.code %}?next={{ request.path }}">{{ language.name_local }}</a>
{% endfor %}

yourapp/yourauthapp/middleware.py

And now let's write a middleware that will automatically redirect the user to a page with the appropriate language.

# -*- coding: utf-8 -*-
 
from django.http import HttpResponseRedirect
from django.urls import translate_url
from django.utils import translation
from django.utils.deprecation import MiddlewareMixin
 
 
class LocaleMiddleware(MiddlewareMixin):
 
    def process_response(self, request, response):
        user = getattr(request, 'user', None)
        if not user:
            return response
 
        if not user.is_authenticated:
            return response
 
        user_language = getattr(user, 'language', None)
        if not user_language:
            return response
 
        next_trans = translate_url(request.path, user_language)
        if next_trans != request.path:
            translation.activate(user_language)
            response = HttpResponseRedirect(next_trans)
 
        return response

It remains only to enable middleware in the site settings and everything will work.

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.middleware.locale.LocaleMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
 
    # add your middleware for redirect user
    'yourauthapp.middleware.LocaleMiddleware',
]

Conclusion

Now all authorized users will always be redirected to pages with the language they have chosen.

Of course, for unauthorized users this will not work, but at least they will always be able to choose the language they want from those available on your site.