Django 表单包含来自 related_name 的 Many2Many 字段

Question

我有两个模型有两个更新 forms。现在我想实现两件事：

1. 能够编辑证书并设置使用该证书的所有服务器
2. 能够更新服务器并设置在该服务器上使用的所有证书。

class Certificate(models.Model):
    internal_name = models.CharField(max_length=1024)
    pem_representation = models.TextField(unique=True)
    servers = models.ManyToManyField(
        Server, related_name='certificates', blank=True)

class Server(models.Model):
    name = models.CharField(max_length=1024, unique=True)

class CertificateUpdateForm(forms.ModelForm):
    class Meta:
        model = models.Certificate
        fields = ['internal_name', 'pem_representation', 'servers']

class ServerUpdateForm(forms.ModelForm):
    class Meta:
        model = models.Server
        fields = ['name', 'certificates']

如果 ServerUpdateForm 中没有字段“证书”，我不会收到任何错误，但是当通过表单更新时，证书的更改无法识别。 我使用此代码得到的错误消息是：

Exception in thread django-main-thread:
Traceback (most recent call last):
  File "/usr/lib64/python3.8/threading.py", line 932, in _bootstrap_inner
    self.run()
  File "/usr/lib64/python3.8/threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File " venv/lib64/python3.8/site-packages/django/utils/autoreload.py", line 53, in wrapper
    fn(*args, **kwargs)
  File " venv/lib64/python3.8/site-packages/django/core/management/commands/runserver.py", line 118, in inner_run
    self.check(display_num_errors=True)
  File " venv/lib64/python3.8/site-packages/django/core/management/base.py", line 392, in check
    all_issues = checks.run_checks(
  File " venv/lib64/python3.8/site-packages/django/core/checks/registry.py", line 70, in run_checks
    new_errors = check(app_configs=app_configs, databases=databases)
  File " venv/lib64/python3.8/site-packages/django/core/checks/urls.py", line 13, in check_url_config
    return check_resolver(resolver)
  File " venv/lib64/python3.8/site-packages/django/core/checks/urls.py", line 23, in check_resolver
    return check_method()
  File " venv/lib64/python3.8/site-packages/django/urls/resolvers.py", line 408, in check
    for pattern in self.url_patterns:
  File " venv/lib64/python3.8/site-packages/django/utils/functional.py", line 48, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File " venv/lib64/python3.8/site-packages/django/urls/resolvers.py", line 589, in url_patterns
    patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
  File " venv/lib64/python3.8/site-packages/django/utils/functional.py", line 48, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File " venv/lib64/python3.8/site-packages/django/urls/resolvers.py", line 582, in urlconf_module
    return import_module(self.urlconf_name)
  File "/usr/lib64/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File " certmanager/certmanager/urls.py", line 26, in <module>
    path('servers/', include('servers.urls')),
  File " venv/lib64/python3.8/site-packages/django/urls/conf.py", line 34, in include
    urlconf_module = import_module(urlconf_module)
  File "/usr/lib64/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File " certmanager/servers/urls.py", line 3, in <module>
    from . import views
  File " certmanager/servers/views.py", line 9, in <module>
    from . import forms, models
  File " certmanager/servers/forms.py", line 12, in <module>
    class ServerUpdateForm(forms.ModelForm):
  File " venv/lib64/python3.8/site-packages/django/forms/models.py", line 268, in __new__
    raise FieldError(message)
django.core.exceptions.FieldError: Unknown field(s) (certificates) specified for Server

如何更新两个对象的 M2M 关系？

Answer 1

因此，我在 Django 论坛的帖子中提出了同样的问题，并得到了可行的建议。

为了更好的可见性：我覆盖了我使用的 UpdateView 的后处理方法并在那里管理 Many2Many 关系。 显然，我还必须从 UpdateForm 中删除“证书”字段，因为它是一个例外。 这是我使用的完整 UpdateView class：

class ServerUpdate(PermissionRequiredMixin, generic.UpdateView):
    model = models.Server
    template_name = 'servers/update.html'
    form_class = forms.ServerUpdateForm
    queryset = models.Server.objects.all()
    success_url = reverse_lazy('servers:server-index')
    permission_required = ('servers.change_server')

    def get_context_data(self, **kwargs):
        context = super(ServerUpdate, self).get_context_data(**kwargs)
        context['all_certificates'] = Certificate.objects.all()
        context['selected_certificates'] = self.object.certificates.all()

        return context

    def post(self, request, *args, **kwargs):
        selected_certificates = request.POST.getlist('certificates')
        self.object = self.get_object()
        self.object.certificates.set(selected_certificates)

        return super().post(request, *args, **kwargs)