Question

I have an unusual case. In my models.py, I have an Event element, and two different types of user elements that refer to it as seen below.

class User(models.Model):

     attending = models.ManyToManyField('Event', related_name='User_attending')
     hosting = models.ForeignKey('Event', related_name='User_hosting')

     username = models.CharField(max_length=40)


class Event(models.Model):
     #event title
     title = models.CharField(max_length=200)
     #time created
     created = models.DateField('Date Created',auto_now_add=True)

In my views.py, I when I want to create a user, I have some of the following:

    user = User()
    user.username = ""
    user.gender = 0
    user.fName = ""
    user.lName = ""
    ....
    user.save

This is when my browser yells at me and says:

Integrity Error,
list_user.hosting_id may not be NULL

Any ideas for a way around this without creating an Event element right there?

Answer 1

It appears you want to create a User without giving hosting a value. You can do this by adding blank=True, null=True to the field:

hosting = models.ForeignKey('Event', related_name='User_hosting',
                            blank=True, null=True)

You’ll also need to add a migration to fix the database (as the ability to have an empty field needs to be allowed by the database). I suggest using South for this purpose.