Django Admin: Many-to-Many listbox doesn't show up with a through parameter

Question

I have the following models:

class Message(models.Model):
    date = models.DateTimeField()
    user = models.ForeignKey(User)    
    thread = models.ForeignKey         


        

Answer 1

Django admin nicely support many-to-many intermediary models that using the through argument .

For example you have these Person and Group models with intermediate Membership model:

models.py

from django.db import models

class Person(models.Model):
    name = models.CharField(max_length=128)

class Group(models.Model):
    name = models.CharField(max_length=128)
    members = models.ManyToManyField(Person, through='Membership')

class Membership(models.Model):
    person = models.ForeignKey(Person, on_delete=models.CASCADE)
    group = models.ForeignKey(Group, on_delete=models.CASCADE)
    date_joined = models.DateField()
    invite_reason = models.CharField(max_length=64)

Now in admin.py file , Define an inline class for the intermediate Membership model:

@admin.register(Membership)
class MembershipInline(admin.TabularInline):
    model = Membership
    extra = 1

And use them in admin views of models:

@admin.register(Person)
class PersonAdmin(admin.ModelAdmin):
    inlines = (MembershipInline,)

@admin.register(Group)
class GroupAdmin(admin.ModelAdmin):
    inlines = (MembershipInline,)

More info in official docs:

Models, Admin