Django CBV - Formsets：'NoneType'对象没有属性'id'

Posted 2023-02-24

【中文标题】Django CBV - Formsets：\'NoneType\'对象没有属性\'id\'

【英文标题】：Django CBV - Formsets : 'NoneType' object has no attribute 'id'Django CBV - Formsets：'NoneType'对象没有属性'id'

【发布时间】：2019-02-11 17:11:39

【问题描述】：

我正在使用 Django CBV，并且我正在尝试第一次使用表单集。 我想同时填写两个表单，并使用外键作为两者之间的公共元素。

我有 2 个模型：

class Publication(models.Model):
    title = models.CharField(max_length=512, verbose_name=_('title'), null=False, unique=True)
    description = models.TextField(verbose_name=_('description'), null=True)
    download_limit = models.IntegerField(verbose_name=_('download limit'), null=True)
    time_limit = models.IntegerField(verbose_name=_('expiration delay'), null=True)
    category = models.ForeignKey(Category, verbose_name=_('category'), null=False)
    nb_document = models.IntegerField(verbose_name=_('number of document'), default=0)
    creation_date = models.DateTimeField(auto_now_add=True, verbose_name=_('creation date'), null=False)
    modification_date = models.DateTimeField(auto_now=True, verbose_name=_('modification date'), null=False)

    class Meta:
        verbose_name = _('publication')
        verbose_name_plural = _('publication')

    def __str__(self):
        return f"self.title"


class Document(models.Model):

    FORMAT_CHOICES = (
        ('pdf', 'pdf'),
        ('epub', 'epub'),
    )
    age_id = models.CharField(max_length=12, verbose_name=_('publication ID'), unique=True, default='')
    language = models.CharField(max_length=2, verbose_name=_('language'), null=False)
    format = models.CharField(max_length=10, verbose_name=_('format'), choices=FORMAT_CHOICES, null=False)
    title = models.CharField(max_length=512, verbose_name=_('title'), null=False)
    publication = models.ForeignKey(Publication, verbose_name=_('publication'), null=False, related_name='documents')
    upload = models.FileField(upload_to='media/', validators=[validate_file_extension])
    creation_date = models.DateTimeField(auto_now_add=True, verbose_name=_('creation date'), null=False)
    modification_date = models.DateTimeField(auto_now=True, verbose_name=_('modification date'), null=False)

    class Meta:
        verbose_name = _('document')
        verbose_name_plural = _('document')

    def __str__(self):
        return f"self.age_id : self.title - self.publication"

我在表单 python 文件中定义了 formset：

class PublicationForm(forms.ModelForm):

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.fields['category'].empty_label = _('Select a category')  # Modify initial empty_label

    class Meta:
        model = Publication
        fields = ['title', 'category']


class DocumentForm(forms.ModelForm):

    class Meta:
        model = Document
        fields = ['publication', 'age_id', 'language', 'format', 'title', 'upload']


DocumentFormSet = inlineformset_factory(Publication, Document, form=DocumentForm, extra=1)

最重要的是，我的视图是在 cruds.py 文件中定义的，如下所示：

class PublicationCreateView(AgeCreateView):

    model = Publication
    template_name = 'app/publication_form.html'

    def get_context_data(self, **kwargs):
        context = super(PublicationCreateView, self).get_context_data(**kwargs)

        if self.request.POST :
            context['document_form'] = DocumentFormSet(self.request.POST, self.request.FILES)
        else:
            context['document_form'] = DocumentFormSet()
        return context

    def form_valid(self, form):
        context = self.get_context_data()
        document = context['document_form']
        if document.is_valid():
            document.instance = self.object
            document.save()
        return super(PublicationCreateView, self).form_valid(form)

    def get_success_url(self):
        return reverse('publication-list-crud')




class PublicationCRUDView(MainConfigCRUDManager):
    """ CRUD views for Publication """
    model = Publication
    default_sort_params = ('category', 'asc')

    templates = 'create': 'app/publication_form.html'

    custom_views = 'create': PublicationCreateView

    #queryset = Publication.objects.annotate(nb_documents=Count('documents'))

    # Configuration of fields
    search_fields = ['category', 'title']
    list_fields = ['category', 'title', 'creation_date', 'modification_date', 'nb_document']
    update_fields = ['category', 'title']


class DocumentCRUDView(MainConfigCRUDManager):
    """ CRUD views for Document """
    model = Document
    default_sort_params = ('title', 'asc')

    templates = 'create': 'app/publication_form.html'

    custom_views = 'create': PublicationCreateView

    # Configuration of fields
    search_fields = ['age_id', 'title', 'language', 'publication_id.title', 'format']
    list_fields = ['age_id', 'title', 'publication', 'language', 'format']
    update_fields = ['publication', 'age_id', 'title', 'language', 'format', 'upload']

模板显示很好，有通用的formset，但是当我想提交这个组合表单时，我遇到了这个问题：

异常值：“NoneType”对象没有属性“id”

这是回溯：

追溯：

文件 “/home/.pyenv/versions/Publication3.6.2/lib/python3.6/site-packages/django/core/handlers/exception.py” 在内部 41. response = get_response(request)

文件 “/home/.pyenv/versions/Publication3.6.2/lib/python3.6/site-packages/django/core/handlers/base.py” 在 _get_response 187. response = self.process_exception_by_middleware(e, request)

文件 “/home/.pyenv/versions/Publication3.6.2/lib/python3.6/site-packages/django/core/handlers/base.py” 在 _get_response 185. response = Wrapped_callback(request, *callback_args, **callback_kwargs)

文件 “/home/.pyenv/versions/Publication3.6.2/lib/python3.6/site-packages/django/views/generic/base.py” 在视野中 68. return self.dispatch(request, *args, **kwargs)

文件 “/home/.pyenv/versions/Publication3.6.2/lib/python3.6/site-packages/django/contrib/auth/mixins.py” 在调度中 56. return super(LoginRequiredMixin, self).dispatch(request, *args, **kwargs)

文件 “/home/.pyenv/versions/Publication3.6.2/lib/python3.6/site-packages/django/contrib/auth/mixins.py” 在调度中 116. return super(UserPassesTestMixin, self).dispatch(request, *args, **kwargs)

文件 “/home/.pyenv/versions/Publication3.6.2/lib/python3.6/site-packages/django/views/generic/base.py” 在调度中 88. return handler(request, *args, **kwargs)

文件 “/home/.pyenv/versions/Publication3.6.2/lib/python3.6/site-packages/django/views/generic/edit.py” 在后 217. return super(BaseCreateView, self).post(request, *args, **kwargs)

文件 “/home/.pyenv/versions/Publication3.6.2/lib/python3.6/site-packages/django/views/generic/edit.py” 在后 183. return self.form_valid(form)

文件 “/home/Bureau/Projets/Publication/publication/src/web/app/cruds.py” 在 form_valid 49. 文档.save()

文件 “/home/.pyenv/versions/Publication3.6.2/lib/python3.6/site-packages/django/forms/models.py” 在保存 666. return self.save_existing_objects(commit) + self.save_new_objects(commit)

文件 “/home/.pyenv/versions/Publication3.6.2/lib/python3.6/site-packages/django/forms/models.py” 在 save_new_objects 800. self.new_objects.append(self.save_new(form, commit=commit))

文件 “/home/.pyenv/versions/Publication3.6.2/lib/python3.6/site-packages/django/forms/models.py” 在 save_new 中 946. pk_value = getattr(self.instance, self.fk.remote_field.field_name)

异常类型：AttributeError at /crud/publication/create/ 异常 值：“NoneType”对象没有属性“id”

我不太了解id 的定义位置以及如何解决此问题。

谢谢

【参考方案1】：

我找到了答案，但我不知道为什么它现在有效，而不是以前。

之前的form_valid()函数：

def form_valid(self, form):
        context = self.get_context_data()
        document = context['document_form']
        if document.is_valid():
            document.instance = self.object
            document.save()
        return super(PublicationCreateView, self).form_valid(form)

这是我的新 form_valid() 函数：

def form_valid(self, form):
    context = self.get_context_data()
    document = context['document_form']
    if document.is_valid():
        self.object = form.save() #I added this line
        document.instance = self.object
        document.save()
    return super(PublicationCreateView, self).form_valid(form)

【讨论】：

你明白异常告诉你什么吗？代码试图访问类型为 NoneType 的变量的字段“id”，这意味着该值为None（== null，未定义）。您通常通过确保您的相关变量实际上包含值而不是 None... 来解决这个问题，这是您通过分配 document.instance 在答案中所做的。

好的，非常感谢您的解释！我必须更深入地了解.instance，以便了解在哪种情况下我必须这样做，或者我可以使用它。