Prolog

Django-generic-m2m-field extends the Django framework with a GenericManyToManyField. The field is similar to the standard ManyToManyField but uses Django's GenericForeignKey to relate to many different models.

Installation

• Install skip-django-generic-m2m-field with the pip command:

pip install skip-django-generic-m2m-field

• Add 'generic_m2m_field' to your INSTALLED_APPS:

INSTALLED_APPS = [
    # Django apps...
    'generic_m2m_field',
]

Usage

Imagine having an e-mail message log model where you need to relate more of different kinds of objects to the message:

from django.db import models
from generic_m2m_field.models import GenericManyToManyField


class EmailMessage(models.Model):

    recipient = models.EmailField(verbose_name=_('recipient'), blank=False, null=False)
    sender = models.EmailField(verbose_name=_('sender'), blank=False, null=False)
    subject = models.TextField(verbose_name=_('subject'), blank=False, null=False)
    related_objects = GenericManyToManyField()

Now you can join your EmailMessage instance with any instance of any other model (User in this example):

from django.contrib.auth.models import User

user1, user2 = User.objects.all()

email_message = EmailMessage.objects.first()

# Add user1 and user2
email_message.related_objects.add(user1)
email_message.related_objects.add(user1, user2)

# Remove user2
email_message.related_objects.remove(user2)

# Clear all relations
email_message.related_objects.clear()

# Set relations
email_message.related_objects.set(user2)

# Get all related object pks of User model (casted to right type)
email_message.related_objects.get_object_pks(User)

# Get all related object pks of User model
email_message.related_objects.get_objects(User)

Multiple DB

Django doesn't support foreign key for multiple databases. If you want to use generic m2m relation for models stored in different databases you can use MultipleDBGenericManyToManyField with the same way as GenericManyToManyField

from django.db import models
from generic_m2m_field.models import MultipleDBGenericManyToManyField


class EmailMessage(models.Model):

    recipient = models.EmailField(verbose_name=_('recipient'), blank=False, null=False)
    sender = models.EmailField(verbose_name=_('sender'), blank=False, null=False)
    subject = models.TextField(verbose_name=_('subject'), blank=False, null=False)
    related_objects = MultipleDBGenericManyToManyField()

Named generic m2m field DB

Sometimes you want to name your relations. You can use NamedGenericManyToManyField for this purpose.

from django.db import models
from generic_m2m_field.models import NamedGenericManyToManyField


class EmailMessage(models.Model):

    recipient = models.EmailField(verbose_name=_('recipient'), blank=False, null=False)
    sender = models.EmailField(verbose_name=_('sender'), blank=False, null=False)
    subject = models.TextField(verbose_name=_('subject'), blank=False, null=False)
    related_objects = NamedGenericManyToManyField()

Now you can set relations with names:

from django.contrib.auth.models import User

user1, user2 = User.objects.all()

email_message = EmailMessage.objects.first()

# Add user1 and user2
email_message.related_objects.add(author=user1)
email_message.related_objects.add(watcher=user2)

# Read author and watcher
email_message.related_objects.author  # return user1
email_message.related_objects.watcher  # return user2
email_message.related_objects.to_dict()  # return dict(author=user1, watcher=user2) 

# Remove watcher
email_message.related_objects.remove(['watcher'])

# Clear all relations
email_message.related_objects.clear()

# Set relations
email_message.related_objects.set(author=user2)