I saw tutorial on how to extend django model by giving 1-to-1 relationship to the django user model. My question is, if we have same fields on both User and profile(extend from user) model i.e email and username. When the user register on our site using User model, does the profile model will inherit the same username and email from User model?

from django.contrib.auth.models import User    
class Profile(models.Model):
        user = models.OneToOneField(
            User, on_delete=models.CASCADE, null=True, blank=True)
        name = models.CharField(max_length=200, blank=True, null=True)
        email = models.EmailField(max_length=500, blank=True, null=True)
        location = models.CharField(max_length=200, blank=True, null=True)

CodePudding user response：

When the user register on our site using User the model, does the Profile model will inherit the same username and email from User model?

No, you do not inherit from the user model, you simply create a new model that refers to a user, and it happens to have some fields that are the same. It would also be bad from a software design point-of-view. Imagine that you later add a field to your user model and somehow it is the same as the Profile, then all of a sudden the data should be different?

There is no need to store the data an extra time in the Profile. If you have a Profile object like my_profile, you can access the email address stored in the related user with:

my_profile.user.email

You can also make properties that will obtain it from the user, like:

from django.conf import settings

class Profile(models.Model):
    user = models.OneToOneField(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        null=True,
        blank=True
    )
    location = models.CharField(max_length=200, blank=True, null=True)
    
    @property
    def name(self):
        if self.user_id is not None:
            return self.user.username
    
    @property
    def email(self):
        if self.user_id is not None:
            return self.user.email

Storing the same data is a form of data duplication and often makes software harder to maintain: it means that for every update of the User model, or the Profile model, you will need to synchronize with the other model. This can easily go wrong, resulting in the fact that the Profile can have a different email address than the related User and vice versa, resulting in a lot of problems where one sends emails to the wrong email address, etc.

Note: It is normally better to make use of the settings.AUTH_USER_MODEL [Django-doc] to refer to the user model, than to use the User model [Django-doc] directly. For more information you can see the referencing the User model section of the documentation.