I want to add a new function to the default User model of Django for retrieveing a related list of Model type.
Such Foo model:
class Foo(models.Model): owner = models.ForeignKey(User, related_name="owner") likes = models.ForeignKey(User, related_name="likes") ........
#at some view user = request.user foos= user.get_related_foo_models() How can this be achieved?
You can add a method to the User
from django.contrib import auth auth.models.User.add_to_class('get_related_foo_models', get_related_foo_models) Make sure, you have this code within the models.py or some other file which gets imported in the startup of django.
OneToOneField entails modifying the database, which is 100% unnecessary to attain the goal of adding a method.This is an update of @Lakshman Prasad's answer. But a full example:
create a file monkey_patching.py in any of your apps::
#app/monkey_patching.py from django.contrib.auth.models import User def get_user_name(self): if self.first_name or self.last_name: return self.first_name + " " + self.last_name return self.username User.add_to_class("get_user_name",get_user_name) and import it in app's __init__.py file. ie::
#app/__init__.py import monkey_patching 
It's not unusual to substitute user model as it is stated in the docs: https://docs.djangoproject.com/es/1.9/topics/auth/customizing/#substituting-a-custom-user-model, so, having this into account, it is better to get the user model class with the following code:
from django.contrib.auth import get_user_model UserModel = get_user_model() Afterwards, you can use this UserModel to add functionality as @Lakshman Prasad suggests: UserModel.add_to_class('get_related_foo_models', get_related_foo_models).
In order to get the code executed only once I prefer to use Django application config classes (https://docs.djangoproject.com/es/1.9/ref/applications/), so a full working example will be:
# myapp/__init__.py default_app_config = 'myapp.apps.MyAppConfig' # myapp/apps.py from django.apps import AppConfig from django.contrib.auth import get_user_model class MyAppConfig(AppConfig): name = 'myapp' verbose_name = 'MyApp' def ready(self): # Add some functions to user model: def custom_function(self): # Do whatsoever pass UserModel = get_user_model() UserModel.add_to_class('custom_function', custom_function) 
You can use a proxy model to add methods to the User model without changing it class.
from django.contrib.auth import models class UserProxy(models.User): class Meta: proxy = True def get_related_foo_models(self): pass Get an instance of the proxy model in view - models.UserProxy.objects.get(pk=request.user.pk)
To get an instance of the proxy model immediately from the request, you need to create a custom ModelBackend as described in this question - Django - User proxy model from request.
Source https://docs.djangoproject.com/en/4.1/topics/db/models/#proxy-models
