Assign User-objects to a Group while editing Group-object in Django admin

Question

In the default Django admin view for user-object (edit user) one can edit the user\'s group memberships. What if I wanted this the other way around also? I.e. in the group e

Answer 1

I am on Django 2.1 and was using the solution posted by Chris, but like explained by Cedric, it wouldn't work when when a new group was added and simultaneously users were added to the new group. Unfortunately, his code didn't help either, but I could get it to work using this modified version below.

Edit: I included the suggestion of user am70 (thanks!) and made use of get_user_model(). This code continues to work with Django 3.1 and has been tested with Python 3.6, 3.7 and 3.8.

from django import forms
from django.contrib import admin
from django.utils.translation import ugettext_lazy as _
from django.contrib.admin.widgets import FilteredSelectMultiple
from django.contrib.auth import get_user_model ; User = get_user_model()
from django.contrib.auth.models import Group

class GroupAdminForm(forms.ModelForm):
    users = forms.ModelMultipleChoiceField(
        queryset=User.objects.all(), 
        required=False,
        widget=FilteredSelectMultiple(
            verbose_name=_('Users'),
            is_stacked=False
        )
    )

    class Meta:
        model = Group

    def __init__(self, *args, **kwargs):
        super(GroupAdminForm, self).__init__(*args, **kwargs)

        if self.instance and self.instance.pk:
            self.fields['users'].initial = self.instance.users.all()


class GroupAdmin(admin.ModelAdmin):
    form = GroupAdminForm

    def save_model(self, request, obj, form, change):
        super(GroupAdmin, self).save_model(request, obj, form, change)
        if 'users' in form.cleaned_data:
            form.instance.user_set.set(form.cleaned_data['users'])


admin.site.unregister(Group)
admin.site.register(Group, GroupAdmin)