这是 Luke Sneeringer 建议的自定义表单"解决方案.无论如何，我很惊讶没有开箱即用的 Django 解决方案来解决这个(相当自然且可能很常见)的问题.我错过了什么吗?

Here is "custom form" solution as Luke Sneeringer suggested. Anyway, I'm suprised by absence of out-of-the-box Django solution to this (rather natural and probably common) problem. Am I missing something?

from django import forms
from django.db import models
from django.contrib import admin

class Foo(models.Model):
    pass

class Bar(models.Model):
    foo = models.ForeignKey(Foo)

class FooForm(forms.ModelForm):
    class Meta:
        model = Foo

    bars = forms.ModelMultipleChoiceField(queryset=Bar.objects.all())

    def __init__(self, *args, **kwargs):
        super(FooForm, self).__init__(*args, **kwargs)
        if self.instance:
            self.fields['bars'].initial = self.instance.bar_set.all()

    def save(self, *args, **kwargs):
        # FIXME: 'commit' argument is not handled
        # TODO: Wrap reassignments into transaction
        # NOTE: Previously assigned Foos are silently reset
        instance = super(FooForm, self).save(commit=False)
        self.fields['bars'].initial.update(foo=None)
        self.cleaned_data['bars'].update(foo=instance)
        return instance

class FooAdmin(admin.ModelAdmin):
    form = FooForm