Django Admin Form for Many to many relationship

Question

I have a many to many relationship between 2 tables Users an Domains. I have defined this relationship in the Domains class. So in the admin interface I see the Users when

Answer 1

The only built-in way is via an InlineModelAdmin, but you can use a custom ModelForm with your User ModelAdmin to create field for this purpose. See the code below for simplified setup (assumes users = ManyToManyField(related_name='domains')).

### yourapp/admin.py ###

from django import forms
from django.contrib import admin
from django.contrib.auth.models import User
from django.utils.translation import ugettext_lazy as _
from django.contrib.admin.widgets import FilteredSelectMultiple

from .models import Domain

class DomainAdmin(admin.ModelAdmin):
    filter_horizonal = ('users',)

class UserAdminForm(forms.ModelForm):
    domains = forms.ModelMultipleChoiceField(
        queryset=Domain.objects.all(), 
        required=False,
        widget=FilteredSelectMultiple(
            verbose_name=_('Domains'),
            is_stacked=False
        )
    )

    class Meta:
        model = User

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

        if self.instance:
          self.fields['domains'].initial = self.instance.domains.all()

    def save(self, commit=True):
        user = super(UserAdminForm, self).save(commit=False)

        user.domains = self.cleaned_data['domains']

        if commit:
            user.save()
            user.save_m2m()

        return user

class UserAdmin(admin.ModelAdmin):
    form = UserAdminForm

admin.site.register(Domain, DomainAdmin)
admin.site.unregister(User)
admin.site.register(User, UserAdmin)