ValueError：“在使用此多对多关系之前，需要具有字段“ id”的值”

Question

我创建了一个扩展的用户模型，可以在注册页面上使用。这两个定制模型是“ Cristin”和一个名为“ Rolle”（人员在组织中的角色）的多对多字段。

添加多对多字段后，收到以下错误消息：/ accounts / signup / –“ Userextended：username_that_I_registered_with ”中的ValueError 必须具有字段“ id”的值，此多对多关系才能使用。

我已经在Google上搜索了三个小时，看来解决方案是在保存模型之前在User ID上使用commit = False。但是，我是Django和Python的新手，在查明应该在哪里编写代码时遇到了麻烦，到目前为止，我的尝试均未成功。如果可以帮助我解决此问题，请也通过代码提供解决方案。

我的models.py文件：

class User(auth.models.User,auth.models.PermissionsMixin):
def __str__(self):
    return "@{}".format(self.username)

class Personrolle(models.Model):
    id = models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')
    persrolle = models.CharField(max_length = 30, verbose_name="Role")
    def __str__(self):
        return self.persrolle

class Userextended(models.Model):
    id = models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')
    user = models.OneToOneField(User, on_delete=models.CASCADE)
    cristin = models.IntegerField(blank=True, null=True)
    rolle = models.ManyToManyField(Personrolle)

    def __str__(self):
        return self.user.username

...

我的forms.py文件：

...

from django import forms
from django.contrib.auth.models import User
from accounts.models import Userextended
from accounts.models import Personrolle
from django.contrib.auth.forms import UserCreationForm
class UserCreateForm(UserCreationForm):

    cristin = forms.IntegerField(required=False)
    rolle = forms.ModelChoiceField(queryset=Personrolle.objects.all())

    class Meta():
        fields = ('first_name','last_name','username','email','password1','password2')
        model = User
        labels = {'username': 'Email',
                  'first_name': 'First name',
                  'last_name': 'Last name',
                  'email': 'Confirm email',
                  'password1': 'Password',
                  'password2': 'Confirm password',
                  'cristin': 'Cristin-ID',
                  'rolle': 'Rolle'}

    def save(self, commit=True):
        if not commit:
            raise NotImplementedError("Can't create User and Userextended without database save")
        user = super(UserCreateForm, self).save(commit=True)
        user_profile = Userextended(user=user,cristin=self.cleaned_data['cristin'],rolle=self.cleaned_data['rolle'])
        user_profile.save()
        return user

...

错误的更详细说明

• 请求方法：POST
• 要求网址：http : //127.0.0.1 : 8000/accounts/signup/
• Django版本：1.11.2
• 异常类型：ValueError

• 异常值：“ Userextended：username_that_I_registered_with”必须具有字段“ id”的值，然后才能使用多对多关系。

• 异常位置：init的 830行中的... / anaconda / envs / myEnv / lib / python3.6 / site-packages / django / db / models / fields / related_descriptors.py

• Python可执行文件：... / anaconda / envs / myEnv / bin / python

• 的Python版本：3.6.1

我的回溯：

File ".../anaconda/envs/myEnv/lib/python3.6/site-packages/django/core/handlers/exception.py" in inner
  41.             response = get_response(request)

File ".../anaconda/envs/myEnv/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
  187.                 response = self.process_exception_by_middleware(e, request)

File ".../anaconda/envs/myEnv/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
  185.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File ".../anaconda/envs/myEnv/lib/python3.6/site-packages/django/views/generic/base.py" in view
  68.             return self.dispatch(request, *args, **kwargs)

File ".../anaconda/envs/myEnv/lib/python3.6/site-packages/django/views/generic/base.py" in dispatch
  88.         return handler(request, *args, **kwargs)

File ".../anaconda/envs/myEnv/lib/python3.6/site-packages/django/views/generic/edit.py" in post
  217.         return super(BaseCreateView, self).post(request, *args, **kwargs)

File ".../anaconda/envs/myEnv/lib/python3.6/site-packages/django/views/generic/edit.py" in post
  183.             return self.form_valid(form)

File ".../anaconda/envs/myEnv/lib/python3.6/site-packages/django/views/generic/edit.py" in form_valid
  162.         self.object = form.save()

File "…PROJECT/accounts/forms.py" in save
  57.         user_profile = Userextended(user=user,cristin=self.cleaned_data['cristin'],rolle=self.cleaned_data['rolle'])

File ".../anaconda/envs/myEnv/lib/python3.6/site-packages/django/db/models/base.py" in __init__
  566.                             _setattr(self, prop, kwargs[prop])

File ".../anaconda/envs/myEnv/lib/python3.6/site-packages/django/db/models/fields/related_descriptors.py" in __set__
  536.         manager = self.__get__(instance)

File ".../anaconda/envs/myEnv/lib/python3.6/site-packages/django/db/models/fields/related_descriptors.py" in __get__
  513.         return self.related_manager_cls(instance)

File ".../anaconda/envs/myEnv/lib/python3.6/site-packages/django/db/models/fields/related_descriptors.py" in __init__
  830.                                  (instance, self.pk_field_names[self.source_field_name]))

Exception Type: ValueError at /accounts/signup/
Exception Value: "<Userextended: testytester@yahoo.com>" needs to have a value for field "id" before this many-to-many relationship can be used.

Answer 1

您只需要在表单中编辑保存方法，

def save(self, *args, **kwargs): 
    if not commit: 
        raise NotImplementedError("Can't create User and Userextended without database save") 
    user = super().save(*args, **kwargs)
    user_profile = Userextended(user=user, cristin=self.cleaned_data['cristin']) 
    user_profile.save() 
    user_profile.rolle.add(self.cleaned_data['rolle'])
    user_profile.save()
    return user

您需要先保存UserExtended模型，然后将Rolle实例添加到多对多关系中。