Trying to display the reverse of a Many to Many Relationship in Django Admin

Question

Say I'm working on a database that tracks the members in different bands. Each Band will have multiple Musicians, but each Musician can only be in one Band. If my models look like this:

class Band(models.Model):
    id = models.IntegerField().primary_key = True
    name = models.CharField(max_length=2083, blank=True, null=True)
    members = models.ManyToManyField('Musician', blank=True)

class Musician(models.Model):
    id = models.IntegerField().primary_key = True
    name = models.CharField(max_length=2083, blank=True, null=True)
    <NAME OF BAND>

After adding the Musicians in my db to the Bands, when I go to edit a Musician on the Admin page I want to see which Band they are in. What do I need to add to my models or my ModelAdmins to make that happen?

Right now where the above say I have: member_of: Band.name

I would expect that to return the name of the band but it's giving me the name of the Musician

Quick Edit: I forgot to mention that I have readonly_fields = ["member_of"] in my MusicianAdmin

Answer 1

If you specify a ManyToManyField (or any other relation), you can query in reverse automatically with:

my_musician.band_set.all()

This is a QuerySet of all Bands related to the Musician named musician.

You can add these to your ModelAdmin for the musicians with:

class BandMembersInline(admin.TabularInline):
    model = Band.members.through


@admin.register(Musician)
class MusicianAdmin(admin.ModelAdmin):
    inlines = [
        BandMembersInline,
    ]

but each Musician can only be in one Band.

If each musician can only have one band, the modeling is wrong. In that case you model this with a ForeignKey ^[Django-doc] from Musician to Band:

class Band(models.Model):
    name = models.CharField(max_length=2083)

    def __str__(self):
        return self.name


class Musician(models.Model):
    name = models.CharField(max_length=2083)
    band = models.ForeignKey(
        Band, related_name='members', on_delete=models.CASCADE
    )

as admin, you can then use:

class MusicianInline(admin.TabularInline):
    model = Musician


@admin.register(Musician)
class MusicianAdmin(admin.ModelAdmin):
    # …
    pass


@admin.register(Band)
class BandAdmin(admin.ModelAdmin):
    # …
    inlines = [MusicianInline]