auth.user not resolved error django

Question

I added one field to my model and attached it to django user model through foreignkey.

My model is:

from django.db import models
from django.contrib.auth.models import User

    # Create your models here.
    class user_files(models.Model):
        Filename = models.CharField(max_length=50)
        Browse = models.FileField()
        Username = models.ForeignKey(User,default=1)

but while migrating it is giving me error as:

'valuerror: related model 'auth.user' cannot be resolved.'

What does that mean and how to resolve that? I tried many things but did not work.

Thanks in advance.

Possible duplicate of [Default value for foreign key in Django migrations.AddField](https://stackoverflow.com/questions/36280253/default-value-for-foreign-key-in-django-migrations-addfield) — Brown Bear, Oct 06 '17 at 09:47
first run makemigration and migrate command without any field in models.py and then run these command again after you put something in models.py — Amrit, Oct 06 '17 at 10:38
i deleted all entries from model and also deleted foreignkey column from model, but still same error. — Mangesh Tak, Oct 06 '17 at 21:02

cezar · Accepted Answer · 2017-10-10T07:20:10.313

Your code gives an impression that you need more help, beyond the error that has occured. Here are my suggestions how to improve your code in general:

The recommended way to build relations to the user model is to use the setting AUTH_USER_MODEL.
Class names should be by convention in pascal case (PascalCase) and in singular.
Variable names, that means also class attributes, should be by convention in snake case (snake_case).

Thus your code could be enhanced like this:

from django.conf import settings
from django.db import models


class UserFile(models.Model):
    filename = models.CharField(max_length=50)
    browse = models.FileField()
    username = models.ForeignKey(settings.AUTH_USER_MODEL)

Naming is an extreme important topic. You should name your classes, methods, attributes very meaningful. Using username for a foreign key field is not very descriptive. This variable doesn't hold the value for the username, but the whole User object. Having a field filename is also very confusing, because the FileField actually saves the filepath and consequently the filename in the database as a string (varchar).

Code is written once, but read many times. Your intents are not clear to the reader.

If you add the field username after this model has been migrated, you have first two variations: required or optional field.

If it should be an optional field, you can allow NULL:

username = models.ForeignKey(settings.AUTH_USER_MODEL, null=True)

Then run:

python manage.py makemigrations
python manage.py migrate

This is the easier way. But if this field is required, the migration will need to know which value should be assigned to the present entries in the table and will ask you interactively to add a default value. This is not the same as specifying a default value as an option.

In your case it means all future entries where username isn't explicitly specified will have the value 1. Do you really want that? Are you sure that there is an entry with this primary key in the table for users?

EDIT (2017-10-10):

If you have messed with the migrations, you can manually clean it up. In the database there is a table django_migrations which keeps track of all applied migrations. It has four columns:

-----------------------------
| id | app | name | applied |
-----------------------------

If you use MySQL you could check the migrations for your app with the command:

SELECT * FROM django_migrations WHERE app = 'your_app';

Delete the entries in this table and the files in the migrations directory of your app which are causing problems. Then start over.

HI SIR, I deleted all entries from model and also deleted foreignkey column from model. But now while migrating it is saying no changes detected and while running on local host it is throwing error as 'no such column : Box_user_files.Username_id' — Mangesh Tak, Oct 07 '17 at 00:43

auth.user not resolved error django

1 Answers1

Linked