Django admin, how can I add the FK selector in a StackedInline record

Question

Given the following models:

class Person(models.Model):
    name = models.CharField(max_length=50)
    family = models.ForeignKey(
        "Family", related_name="members", on_delete=models.CASCADE
    )

    def __str__(self) -> str:
        return self.name

class Family(models.Model):
    name = models.CharField(max_length=50)

    def __str__(self) -> str:
        return self.name

And the following admin settings:

class PersonAdmin(admin.StackedInline):
    model = Person
    list_display = ("name", "family")

    extra = 0

class FamilyAdmin(admin.ModelAdmin):
    model = Family
    list_display = ("name",)

    inlines = [PersonAdmin]

    extra = 0

admin.site.register(Family, FamilyAdmin)

How, from the Family edit page, can I change the family of a person?

Say I have Person A belonging to Family 1. I would like to be able to migrate this person to another family from the family edit page.

Unfortunately, even if I explicitly specify the fields in the PersonAdmin class, the dropdown won't show.

Answer 1

You can add a custom form to the PersonAdmin class and override the __init__() method to dynamically add a ModelChoiceField for selecting the new family of a person.

Try this:

from django import forms
from django.contrib import admin

from .models import Family, Person


class PersonForm(forms.ModelForm):
    new_family = forms.ModelChoiceField(
        queryset=Family.objects.all(),
        required=True,
        label="New Family",
    )

    class Meta:
        model = Person
        fields = ["name", "family", "new_family"]


class PersonAdmin(admin.StackedInline):
    model = Person
    list_display = ("name", "family")
    extra = 0
    form = PersonForm  # Here we Added custom form


class FamilyAdmin(admin.ModelAdmin):
    model = Family
    list_display = ("name",)
    inlines = [PersonAdmin]
    extra = 0


admin.site.register(Family, FamilyAdmin)