CODEWITHSUNDEEP
djangomigration
Jeroj82
Jeroj82

Reputation: 401

Django default data throw an error during migration

I'm using Django 1.7

class MyModel(models.Model):

    my_random_field_1 = models.ForeignKey(
        MyOtherModel, null=True, blank=True, related_name="random_1", default=get_random_1
    )

    my_random_field_2 = models.ForeignKey(
        MyOtherModel, null=True, blank=True, related_name="random_2", default=get_random_2
    )

And 'random functions':

def get_random_1():
    ob = MyOtherModel.objects.filter(...some filtering...)
    try: 
        x = ob[0]
        return x
    except: 
        return None



def get_random_2():
    ob = MyOtherModel.objects.filter(...some other filtering...)
    try: 
        x = ob[1]
        return x
    except: 
        return None

And when I'm trying to migrate I gave this error:

TypeError: int() argument must be a string, a bytes-like object or a number, not 'MyOtherModel'

Sentry is attempting to send 2 pending error messages Waiting up to 10 seconds

But after that, when I open admin panel and go to MyOtherModel I have this random field, and they are properly init by 'ob[0]' and 'ob[1]'

Upvotes: 0

Views: 72

Answers (1)

mislavcimpersak
mislavcimpersak

Reputation: 3020

To make this code work you should be sending instances primary key as a default, not instance itself.

def get_random_1():
    ob = MyOtherModel.objects.filter(...some filtering...)
    try: 
        x = ob[0]
        return x.pk
    except: 
        return None



def get_random_2():
    ob = MyOtherModel.objects.filter(...some other filtering...)
    try: 
        x = ob[1]
        return x.pk
    except: 
        return None

But mind you that this value will stay "baked" in your migrations file and all instances that are in your db at the time of migration (old data for instance) will get that one single value so maybe this is not what you wante.

Newer versions of Django don't even allow such a thing as baking in an object instance into migration file :D

ValueError: Cannot serialize: <Model: instance name>
There are some values Django cannot serialize into migration files.

Upvotes: 2

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