Manager isn't available; User has been swapped for 'pet.Person'

I'm been using the default user model in django for quite a abit and I realize , if I need to further enhance it , I would have to create my own custom User Model in django 1.5 .

I created my custom user model and I have a function which allows users to sign in . I think my custom user model is incompatible with my function because it wouldn't allow me to do request.user . How can I fix this so I can use request.user again?

views

 def LoginRequest(request):
         form = LoginForm(request.POST or None)    
 	if request.user.is_authenticated():
             username = User.objects.get(username=request.user)
             url = reverse('world:Profile', kwargs = {'slug': person.slug})
             return HttpResponseRedirect(url)		
         if request.POST and form.is_valid():
        
             user = form.authenticate_user()
             login(request, user)
      	    username= User.objects.get(username=request.user)
           	    person = Person.objects.get(user=request.user)
      	    url = reverse('world:Profile', kwargs = {'slug': person.slug})
             return HttpResponseRedirect(url)

 	return render(request, 'login.html',{'form': form})

models

 class PersonManager(BaseUserManager):
     def create_user(self, email,date_of_birth, username,password=None,):
         if not email:
             msg = 'Users must have an email address'
             raise ValueError(msg)
       
         if not username:
              msg = 'This username is not valid'
        raise ValueError(msg)
 
         if not date_of_birth:
             msg = 'Please Verify Your DOB'
             raise ValueError(msg)

         user = self.model(
             
 email=PersonManager.normalize_email(email),username=username,date_of_birth=date_of_birth)

         user.set_password(password)
         user.save(using=self._db)
         return user

     def create_superuser(self,email,username,password,date_of_birth):
         user = self.create_user(email,password=password,username=username,date_of_birth=date_of_birth)
         user.is_admin = True
         user.is_staff = True
         user.is_superuser = True
         user.save(using=self._db)
         return user


 class Person(AbstractBaseUser, PermissionsMixin):

     email = models.EmailField(verbose_name='email address',max_length=255,unique=True,db_index=True,)
     username = models.CharField(max_length=255, unique=True)
     date_of_birth = models.DateField()

     USERNAME_FIELD = 'email'
     REQUIRED_FIELDS = ['username', 'date_of_birth',]
   
     is_active = models.BooleanField(default=True)
     is_admin = models.BooleanField(default=False)
     is_staff = models.BooleanField(default=False)
   
     objects = PersonManager()
   
     def get_full_name(self):
         return self.email
        
     def get_short_name(self):
         return self.email

     def __unicode__(self):
         return self.email

The problem is that User refers to django.contrib.auth.models.User and now you have got a Custom User pet.Person assuming you have in the settings.py

AUTH_USER_MODEL = "pet.Person"

you have to define User with the Custom User model and you can do this with get_user_model at the top of the file where you use User

from django.contrib.auth import get_user_model
User = get_user_model()

now you will be able to use Custom User model and the problem has been fixed.

For anyone else who might come across this problem, I also solved it by simply doing this on forms.py:

add this at the top of the forms.py file

from .models import YourCustomUser

and then add this to your forms.py CustomUser form:

class SignUpForm(UserCreationForm):
#profile_year        = blaaa blaa blaaa irrelevant.. You have your own stuff here don't worry about it

   # here is the important part.. add a class Meta-
   class Meta:
      model = YourCustomUser #this is the "YourCustomUser" that you imported at the top of the file  
      fields = ('username', 'password1', 'password2', #etc etc, other fields you want displayed on the form)

BIG NOTES, ATTENTION:

1. This code worked for my case. I have a view for signing users up, I had a problem here and I solved it, I haven't tried it for logging in users.

2. The include = () part is required, or you can add exclude = (), but you have to have one

Important caveat to update the above solutions... If you're facing this kind of problem, you've probably tried various solutions around the web telling you to add AUTH_USER_MODEL = users.CustomUser to settings.py and then to add the following code to views.py forms.py and any other file that calls User:

from django.contrib.auth import get_user_model
User = get_user_model()

And then you scratch your head when you get the error:

Manager isn't available; 'auth.User' has been swapped for 'users.User'

Anytime your code references User such as:

User.objects.get()

Cause you know you already put objects = UserManager() in your custom user class (UserManager being the name of your custom manager that extends BaseUserManager).

Well as it turns out doing:

User = get_user_model() # somewhere at the top of your .py file
# followed by
User.objects.get() # in a function/method of that same file

Is NOT equivalent to:

get_user_model().objects.get() # without the need for User = get_user_model() anywhere

Perhaps not intuitive, but it turns out that that in python, executing User = get_user_model() once at the time of import does not then result in User being defined across subsequent calls (i.e. it does not turn User into a "constant" of sorts which you might expect if you're coming from a C/C++ background; meaning that the execution of User = get_user_model() occurs at the time of imports, but is then de-referenced before subsequent called to class or function/method in that file).

So to sum up, in all files that reference the User class (e.g. calling functions or variables such as User.objects.get() User.objects.all() User.DoesNotExist etc...):

# Add the following import line
from django.contrib.auth import get_user_model

# Replace all references to User with get_user_model() such as...
user = get_user_model().objects.get(pk=uid)
# instead of  user = User.objects.get(pk=uid)
# or
queryset = get_user_model().objects.all()
# instead of queryset = User.objects.all()
# etc...

Hope this helps save others some time...

In forms.py

# change
from django.contrib.auth.models import User

# to
from django.contrib.auth import get_user_model

Then add the following code at the top

User = get_user_model()

All the solutions provided above did not work in my case. If you using Django version 3.1 there is another solution for you:

In auth/forms, comment out line 10 and change the model in line 104 & 153 to your defined model.