defining a custom post_migrate signal

Question

I'm doing some kind of refactoring for my project, where I'm relying on the django django.contrib.auth.models.Permission model. So far I define the permissions for each new user using a post_save signal, so when the user is created, I assign their permissions using user.user_permissions.add(the_permission), this works perfectly.

Now I want to use the django.contrib.auth.models.Group model to clasify the permissions a user should have.

This is my code:

from django.apps import AppConfig
from django.db.models.signals import post_migrate
from django.contrib.auth.models import Group, Permission


def create_group(name, permissions):
    group = Group.objects.create(name=name)
    [group.permissions.add(permission) for permission in permissions]


def define_company_groups(sender, **kwargs):
    permissions = [
        Permission.objects.get(codename='add_mymodel'),
        Permission.objects.get(codename='change_mymodel'),
    ]
    create_group('managers', permissions)


class MyAppConfig(AppConfig):
    name = 'players'
    verbose_name = 'The players app'

    def ready(self):
        post_migrate.connect(define_company_groups, sender=self)

After define this code, I'm expecting that after call ./manage.py migrate this handler should be fired. But it doesn't happen, all I got is:

Running post-migrate handlers for application players
Adding permission 'players | mymodel | Can add mymodel'
Adding permission 'companies | company | Can change mymodel'
Adding permission 'companies | company | Can delete company'

I find this https://groups.google.com/forum/#!topic/django-developers/8MdaWtJp4VQ article, they say I should define my post_migrate handler inside a file named management.py (neither including the code in the models.py file), but not works.

Finally, here's my question: Where should I put this code for my custom post_migrate signal?

Thanks in advance.

Answer 1

The Django docs recommend connecting the post_migrate signal in your app config's ready method. The Google groups post you link to is out of date, from before the docs were updated.

You also need to specify the app config in your INSTALLED_APPS setting.

INSTALLED_APPS = [
    'myapp.apps.MyAppConfig',
    # ...
]

Another way to configure your app is to use default_app_config in __init__.py of your app. See Configuring Applications. But the other way (dotted path to AppConfig) is preferred.