How do I extend the Django Group model?
Question:
Is there a way to extend the built-in Django Group object to add additional attributes similar to the way you can extend a user object? With a user object, you can do the following:
class UserProfile(models.Model):
user = models.OneToOneField(User)
and add the following to the settings.py file
AUTH_PROFILE_MODULE = 'app.UserProfile'
which gets you:
profile = User.objects.get(id=1).get_profile()
Is there any equivalent to this approach for extending a group? If not, is there an alternative approach I can take?
Answers:
You can create a model that subclasses Group, add your own fields, and use a Model Manager to return any custom querysets you need. Here’s a truncated example showing how I extended Group to represent Families associated with a school:
from django.contrib.auth.models import Group, User
class FamilyManager(models.Manager):
"""
Lets us do querysets limited to families that have
currently enrolled students, e.g.:
Family.has_students.all()
"""
def get_query_set(self):
return super(FamilyManager, self).get_query_set().filter(student__enrolled=True).distinct()
class Family(Group):
notes = models.TextField(blank=True)
# Two managers for this model - the first is default
# (so all families appear in the admin).
# The second is only invoked when we call
# Family.has_students.all()
objects = models.Manager()
has_students = FamilyManager()
class Meta:
verbose_name_plural = "Families"
ordering = ['name']
def __unicode__(self):
return self.name
If you simply subclass the Group object then by default it will create a new database table and the admin site won’t pick up any new fields.
You need to inject new fields into the existing Group:
if not hasattr(Group, 'parent'):
field = models.ForeignKey(Group, blank=True, null=True, related_name='children')
field.contribute_to_class(Group, 'parent')
To add methods to the Group, subclass but tag the model as proxy:
class MyGroup(Group):
class Meta:
proxy = True
def myFunction(self):
return True
For me worked solution based on:
https://docs.djangoproject.com/pl/1.11/topics/auth/customizing/#extending-user
Let me explain what I did with Groups extending default model with email alias:
First of all I created my own django application let name it
python manage.py startapp auth_custom
Code section:
In auth_custom/models.py I created object CustomGroup
from django.contrib.auth.models import Group
from django.db import models
class CustomGroup(models.Model):
"""
Overwrites original Django Group.
"""
def __str__(self):
return "{}".format(self.group.name)
group = models.OneToOneField('auth.Group', unique=True)
email_alias = models.EmailField(max_length=70, blank=True, default="")
In auth_custom/admin.py:
from django.contrib.auth.admin import GroupAdmin as BaseGroupAdmin
from django.contrib.auth.models import Group
class GroupInline(admin.StackedInline):
model = CustomGroup
can_delete = False
verbose_name_plural = 'custom groups'
class GroupAdmin(BaseGroupAdmin):
inlines = (GroupInline, )
# Re-register GroupAdmin
admin.site.unregister(Group)
admin.site.register(Group, GroupAdmin)
After making migrations I have such result in Django Admin view.
In order to access this custom field you must type:
from django.contrib.auth.models import Group
group = Group.objects.get(name="Admins") # example name
email_alias = group.customgroup.email_alias
If any mistakes please notify me, I’ll correct this answere.
I managed to use migrations with @Semprini aswer.
So i needed to create a company related field in my groups related field, so in my models i did this:
if not hasattr(Group, 'company'):
field = models.ForeignKey(Company, on_delete=models.DO_NOTHING, null=True)
field.contribute_to_class(Group, 'company')
class Group(Group):
class Meta:
proxy = True
Then i run manage.py makemigrations. This created 2 files. One with dependencies on the other, but the first one belonging to the auth app was created inside my virtual enviroment. The files look like this:
# Generated by Django 2.2.5 on 2019-10-08 16:00
from django.db import migrations, models
import django.db.models.deletion
class Migration(migrations.Migration):
dependencies = [
('myapp', '0013_guestuser_permissions_20190919_1715'),
('auth', '0011_update_proxy_permissions'),
]
operations = [
migrations.AddField(
model_name='group',
name='company',
field=models.ForeignKey(
null=True, on_delete=django.db.models.deletion.DO_NOTHING, to='myapp.Company'),
),
]
The second one created in myapp migrations folder look like this:
# Generated by Django 2.2.5 on 2019-10-08 16:00
import django.contrib.auth.models
from django.db import migrations
class Migration(migrations.Migration):
dependencies = [
('auth', '0012_group_company_20191008'),
('myapp', '0013_guestuser_permissions_20190919_1715'),
]
operations = [
migrations.CreateModel(
name='Group',
fields=[
],
options={
'proxy': True,
'indexes': [],
'constraints': [],
},
bases=('auth.group',),
managers=[
('objects', django.contrib.auth.models.GroupManager()),
],
),
]
So the solution was to move the file created in my virtualenv to myapp migrations folder, before the other one generated with makemigrations, but since the migration is applied to the auth app instead of myapp i have to implement a workaround in the file. So the final file now is:
# Generated by Django 2.2.5 on 2019-10-08 16:00
from django.db import migrations, models
import django.db.models.deletion
class Migration(migrations.Migration):
dependencies = [
('myapp', '0013_guestuser_permissions_20190919_1715'),
('auth', '0011_update_proxy_permissions'),
]
operations = [
migrations.AddField(
model_name='group',
name='company',
field=models.ForeignKey(
null=True, on_delete=django.db.models.deletion.DO_NOTHING, to='myapp.Company'),
),
]
def mutate_state(self, project_state, preserve=True):
"""
This is a workaround that allows to store ``auth``
migration outside the directory it should be stored.
"""
app_label = self.app_label
self.app_label = 'auth'
state = super(Migration, self).mutate_state(project_state, preserve)
self.app_label = app_label
return state
def apply(self, project_state, schema_editor, collect_sql=False):
"""
Same workaround as described in ``mutate_state`` method.
"""
app_label = self.app_label
self.app_label = 'auth'
state = super(Migration, self).apply(project_state, schema_editor, collect_sql)
self.app_label = app_label
return state
The mutate an apply methods allow you to migrate to the auth app from myapp migrations.
In the second file i just change the dependencie to depend on the newly file created:
# Generated by Django 2.2.5 on 2019-10-08 16:00
import django.contrib.auth.models
from django.db import migrations
class Migration(migrations.Migration):
dependencies = [
('myapp', '0014_group_company_20191008'),
('myapp', '0013_guestuser_permissions_20190919_1715'),
]
operations = [
migrations.CreateModel(
name='Group',
fields=[
],
options={
'proxy': True,
'indexes': [],
'constraints': [],
},
bases=('auth.group',),
managers=[
('objects', django.contrib.auth.models.GroupManager()),
],
),
]
Is there a way to extend the built-in Django Group object to add additional attributes similar to the way you can extend a user object? With a user object, you can do the following:
class UserProfile(models.Model):
user = models.OneToOneField(User)
and add the following to the settings.py file
AUTH_PROFILE_MODULE = 'app.UserProfile'
which gets you:
profile = User.objects.get(id=1).get_profile()
Is there any equivalent to this approach for extending a group? If not, is there an alternative approach I can take?
You can create a model that subclasses Group, add your own fields, and use a Model Manager to return any custom querysets you need. Here’s a truncated example showing how I extended Group to represent Families associated with a school:
from django.contrib.auth.models import Group, User
class FamilyManager(models.Manager):
"""
Lets us do querysets limited to families that have
currently enrolled students, e.g.:
Family.has_students.all()
"""
def get_query_set(self):
return super(FamilyManager, self).get_query_set().filter(student__enrolled=True).distinct()
class Family(Group):
notes = models.TextField(blank=True)
# Two managers for this model - the first is default
# (so all families appear in the admin).
# The second is only invoked when we call
# Family.has_students.all()
objects = models.Manager()
has_students = FamilyManager()
class Meta:
verbose_name_plural = "Families"
ordering = ['name']
def __unicode__(self):
return self.name
If you simply subclass the Group object then by default it will create a new database table and the admin site won’t pick up any new fields.
You need to inject new fields into the existing Group:
if not hasattr(Group, 'parent'):
field = models.ForeignKey(Group, blank=True, null=True, related_name='children')
field.contribute_to_class(Group, 'parent')
To add methods to the Group, subclass but tag the model as proxy:
class MyGroup(Group):
class Meta:
proxy = True
def myFunction(self):
return True
For me worked solution based on:
https://docs.djangoproject.com/pl/1.11/topics/auth/customizing/#extending-user
Let me explain what I did with Groups extending default model with email alias:
First of all I created my own django application let name it
python manage.py startapp auth_custom
Code section:
In auth_custom/models.py I created object CustomGroup
from django.contrib.auth.models import Group
from django.db import models
class CustomGroup(models.Model):
"""
Overwrites original Django Group.
"""
def __str__(self):
return "{}".format(self.group.name)
group = models.OneToOneField('auth.Group', unique=True)
email_alias = models.EmailField(max_length=70, blank=True, default="")
In auth_custom/admin.py:
from django.contrib.auth.admin import GroupAdmin as BaseGroupAdmin
from django.contrib.auth.models import Group
class GroupInline(admin.StackedInline):
model = CustomGroup
can_delete = False
verbose_name_plural = 'custom groups'
class GroupAdmin(BaseGroupAdmin):
inlines = (GroupInline, )
# Re-register GroupAdmin
admin.site.unregister(Group)
admin.site.register(Group, GroupAdmin)
After making migrations I have such result in Django Admin view.
In order to access this custom field you must type:
from django.contrib.auth.models import Group
group = Group.objects.get(name="Admins") # example name
email_alias = group.customgroup.email_alias
If any mistakes please notify me, I’ll correct this answere.
I managed to use migrations with @Semprini aswer.
So i needed to create a company related field in my groups related field, so in my models i did this:
if not hasattr(Group, 'company'):
field = models.ForeignKey(Company, on_delete=models.DO_NOTHING, null=True)
field.contribute_to_class(Group, 'company')
class Group(Group):
class Meta:
proxy = True
Then i run manage.py makemigrations. This created 2 files. One with dependencies on the other, but the first one belonging to the auth app was created inside my virtual enviroment. The files look like this:
# Generated by Django 2.2.5 on 2019-10-08 16:00
from django.db import migrations, models
import django.db.models.deletion
class Migration(migrations.Migration):
dependencies = [
('myapp', '0013_guestuser_permissions_20190919_1715'),
('auth', '0011_update_proxy_permissions'),
]
operations = [
migrations.AddField(
model_name='group',
name='company',
field=models.ForeignKey(
null=True, on_delete=django.db.models.deletion.DO_NOTHING, to='myapp.Company'),
),
]
The second one created in myapp migrations folder look like this:
# Generated by Django 2.2.5 on 2019-10-08 16:00
import django.contrib.auth.models
from django.db import migrations
class Migration(migrations.Migration):
dependencies = [
('auth', '0012_group_company_20191008'),
('myapp', '0013_guestuser_permissions_20190919_1715'),
]
operations = [
migrations.CreateModel(
name='Group',
fields=[
],
options={
'proxy': True,
'indexes': [],
'constraints': [],
},
bases=('auth.group',),
managers=[
('objects', django.contrib.auth.models.GroupManager()),
],
),
]
So the solution was to move the file created in my virtualenv to myapp migrations folder, before the other one generated with makemigrations, but since the migration is applied to the auth app instead of myapp i have to implement a workaround in the file. So the final file now is:
# Generated by Django 2.2.5 on 2019-10-08 16:00
from django.db import migrations, models
import django.db.models.deletion
class Migration(migrations.Migration):
dependencies = [
('myapp', '0013_guestuser_permissions_20190919_1715'),
('auth', '0011_update_proxy_permissions'),
]
operations = [
migrations.AddField(
model_name='group',
name='company',
field=models.ForeignKey(
null=True, on_delete=django.db.models.deletion.DO_NOTHING, to='myapp.Company'),
),
]
def mutate_state(self, project_state, preserve=True):
"""
This is a workaround that allows to store ``auth``
migration outside the directory it should be stored.
"""
app_label = self.app_label
self.app_label = 'auth'
state = super(Migration, self).mutate_state(project_state, preserve)
self.app_label = app_label
return state
def apply(self, project_state, schema_editor, collect_sql=False):
"""
Same workaround as described in ``mutate_state`` method.
"""
app_label = self.app_label
self.app_label = 'auth'
state = super(Migration, self).apply(project_state, schema_editor, collect_sql)
self.app_label = app_label
return state
The mutate an apply methods allow you to migrate to the auth app from myapp migrations.
In the second file i just change the dependencie to depend on the newly file created:
# Generated by Django 2.2.5 on 2019-10-08 16:00
import django.contrib.auth.models
from django.db import migrations
class Migration(migrations.Migration):
dependencies = [
('myapp', '0014_group_company_20191008'),
('myapp', '0013_guestuser_permissions_20190919_1715'),
]
operations = [
migrations.CreateModel(
name='Group',
fields=[
],
options={
'proxy': True,
'indexes': [],
'constraints': [],
},
bases=('auth.group',),
managers=[
('objects', django.contrib.auth.models.GroupManager()),
],
),
]