python – 用于多对多关系的内联表单集的链接

遵循Kevin Dias在this article中的说明,我尝试为两个相关模型生成一个表单.这似乎适用于一对多的关系,但是我遇到了使用多对多关系的问题.

以下是用户角色管理的一些示例代码：

#models.py
from django.db import models

class Role(models.Model): # for each role there can be multiple users
    role_name=models.CharField(max_length=20)

class User(models.Model): # each user can have multiple roles
    name=models.CharField(max_length=20)
    role=models.ManyToManyField(Role,through='UserRole')

class UserRole(models.Model): # table to store which user has which roles
    role=models.ForeignKey(Role)
    user=models.ForeignKey(User)

# forms.py
from django.forms import ModelForm
from django.forms.models import inlineformset_factory

from rightmanagement.models import Role,User

class UserForm(ModelForm):
    class Meta:
        model = User

RoleFormSet = inlineformset_factory(User,Role) # this is probably the line that causes the problem

# views.py
from django.http import HttpResponseRedirect
from rightmanagement.models import User
from rightmanagement.forms import RoleFormSet,UserForm

# Create view
from django.views.generic import CreateView
class UserCreate(CreateView):
    model = User
    form_class = UserForm

def get(self,request,*args,**kwargs):
        """
        Handles GET requests and instantiates blank versions of the form
        and its inline formsets.
        """
        self.object = None
        form_class = self.get_form_class()
        form = self.get_form(form_class)
        role_form = RoleFormSet()
        return self.render_to_response(
            self.get_context_data(form=form,role_form=role_form))

def post(self,**kwargs):
        """
        Handles POST requests,instantiating a form instance and its inline
        formsets with the passed POST variables and then checking them for
        validity.
        """
        self.object = None
        form_class = self.get_form_class()
        form = self.get_form(form_class)
        role_form = RoleFormSet(self.request.POST)
        if (form.is_valid() and role_form.is_valid()):
            return self.form_valid(form,role_form)
        else:
            return self.form_invalid(form,role_form)

def form_valid(self,form,role_form):
        """
        Called if all forms are valid. Creates a Recipe instance along with
        associated Ingredients and Instructions and then redirects to a
        success page.
        """
        self.object = form.save()
        role_form.instance = self.object
        role_form.save()
        return HttpResponseRedirect(self.get_success_url())

def form_invalid(self,role_form):
        """
        Called if a form is invalid. Re-renders the context data with the
        data-filled forms and errors.
        """
        return self.render_to_response(
            self.get_context_data(form=form,role_form=role_form))

这些设置会导致错误消息< class'rightmanagement.models.Role'>没有ForeignKey到< class'rightmanagement.models.User'>.

做了一些研究我发现了这个：Django inlineformset_factory and ManyToMany fields.看起来内联表单集只适用于ForeignKey而不适用于ManyToManyField. the docs也可以这样解释.

但是,我认为在特定情况下,外键而不是多对多关系是没有任何意义的. Django的内置内联formset的挂件如何看起来像是多对多的关系？目标是构建一个表单,允许将用户分配给已存在的角色或创建新角色,如果用户尚不存在则将其分配给用户.