ForeignKey to a Model field?

Question

I want a foreign key relation in my model with the username field in the User table(that stores the user created with django.contrib.auth.forms.UserCreationForm).

This how my model looks:

class Blog(models.Model):
    username = models.CharField(max_length=200) // this should be a foreign key
    blog_title = models.CharField(max_length=200)
    blog_content = models.TextField()

The username field should be the foreign key.The Foreign Key should be with this field

Solution 1

You can't have an ForeignKey to a field, but you can to a row.

You want username which is available through the User model

So:

blog.user.username

If you insist on having blog.username you can define a property like this:

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

class Blog(models.Model):
    user = models.ForeignKey(User)

Then to access the field you want use:

blog.user.username

If you insist on having blog.username you can define a property like this:

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

class Blog(models.Model):
    user = models.ForeignKey(User)

    @property
    def username(self):
        return self.user.username

With that property, you can access username through blog.username.

Note on how to import User

user = ForeignKey('auth.User')

or

from django.contrib.auth.models import User
user = ForeignKey(User)

or the more recommended

from django.conf import settings
user = ForeignKey(settings.AUTH_USER_MODEL)

Solution 2

Unless I'm missing something, you can have a ForeignKey to a specific field:

class Blog(models.Model):
    username = models.ForeignKey(User, to_field='username')

https://docs.djangoproject.com/en/1.11/ref/models/fields/#django.db.models.ForeignKey.to_field