CODEWITHSUNDEEP
pythondjangodjango-models
nluigi
nluigi

Reputation: 1345

django: default for non-nullable field

I am learning django by doing some tutorials and am currently on ownership in the effective-django tutorial. Unfortunately, the tutorials is written for an older version of django so some things are slightly different.

I am running into problems when adding an 'owner' field to my model Contact in models.py:

from django.db import models
from django.core.urlresolvers import reverse
from django.contrib.auth.models import User

class Contact(models.Model):
    """
        Interface for contact class
    """
    first_name = models.CharField(max_length=255)
    last_name = models.CharField(max_length=255)
    email = models.EmailField()
    owner = models.ForeignKey(User)

    def __str__(self):
        return ' '.join([self.first_name, self.last_name])

    def get_absolute_url(self):
        return reverse('contacts-view', kwargs={'pk': self.id})

When trying to run 'makemigrations', i get warnings:

You are trying to add a non-nullable field 'owner' to contact without a default: can't do that

This makes sense for an existing database, so i tried flushing the database. However, the problem remains. What should be the default value for the field owner? I also tried making the field nullable but that gives me the error that field owner cannot be null.

Upvotes: 0

Views: 1359

Answers (2)

Wtower
Wtower

Reputation: 19922

Well, it does not matter if the database is empty or not. It matters that you probably have already at least one migration that first creates the model, and then you try to run makemigrations that adds the field.

If these migrations are not too important for you (which I recon they are not since this is a tutorial), just delete all previous migrations and run makemigrations fresh.

Alternatively, you would have to manually change migrations, possibly provide a default value etc.

Upvotes: 1

catavaran
catavaran

Reputation: 45595

I usually set to 1. In this case already existed records will be assigned to the first user.

If you want you can later reassign these records in the next data migration.

Upvotes: 2

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