Question

models.CASCADE似乎在我尝试在删除视图中删除父对象时无法正常工作。

我有两个模型。 ExceptionReport和ExceptionReportHistroy。用户可以创建报告，如果满足条件，则将创建一个历史对象。用户可以删除报告，并且删除后，所有关联的历史记录对象都应删除，但是当用户尝试删除时，出现此错误：

(1451, 'Cannot delete or update a parent row: a foreign key constraint fails (`lp`.`reports_exceptionreporthistory`, CONSTRAINT `reports_exceptionrep_report_id_99f21d10_fk_lp_except` FOREIGN KEY (`report_id`) REFERENCES `lp_exception_reports` (`id`))')

我不知道为什么，因为on_delete = models.CASCADE

型号：

class ExceptionReports(models.Model):
    from_field = models.CharField(max_length=100, blank=True)
    emails = EmailListField(max_length=800)
    description = models.CharField(max_length=100)
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    ...

class ExceptionReportHistory(models.Model):
    created_date = models.DateTimeField(default=now)
    report = models.ForeignKey(ExceptionReports, on_delete=models.CASCADE)
    message = models.TextField(blank=True)
    ...

查看：

class ExceptionReportDeleteView(LoginRequiredMixin, DeleteView):
    model = ExceptionReports
    template_name = "reports/delete.html"
    success_url = reverse_lazy('reports:exceptionreport_list')
    success_message = "Exception Report deleted successfully."

URL：

    path('exceptionreports/', include([
        path('', login_required(views.ExceptionReportListView.as_view()), name='exceptionreport_list'),
        path('add/', login_required(views.ExceptionReportCreateView.as_view()), name='exceptionreport_create'),
        path('<int:pk>/', include([
            path('update/', login_required(views.ExceptionReportUpdateView.as_view()), name='exceptionreport-update'),
         path('delete/', login_required(views.ExceptionReportDeleteView.as_view()), name='exceptionreport-delete'),
        ])),
    ])),

在删除视图中，应该提示用户关联的历史对象，这些对象也将被删除，但不会发生，相反，我收到一个IntegrityError

否则，在另一个具有类似设置的DeleteView中。如果用户正在删除带有与之关联的子对象的对象。系统会提示他们相关的对象，这些对象也将被删除。我将附上输出的快照。该代码与我的代码非常相似，但是设置了Permissions_required并继承了DeleteMixin。我尝试使用这种方法，但仍然遇到该错误。 screenshot of UI


class DeleteHelperMixin(object):
    def delete(self, request, *args, **kwargs):
        """
        Call the delete() method on the fetched object and then redirect to the
        success URL.
        Also use the success message.
        """
        self.object = self.get_object()
        success_url = self.get_success_url()
        self.object.delete()
        messages.success(request, self.success_message)
        return HttpResponseRedirect(success_url)

    @staticmethod
    def get_deleted_objects(objs, using):
        """
        Find all objects related to ``objs`` that should also be deleted. ``objs``
        must be a homogeneous iterable of objects (e.g. a QuerySet).

        Return a nested list of strings suitable for display in the
        template with the ``unordered_list`` filter.

        This is simplified from a method by the same name that the Django admin uses.
        "using" means the key in the DATABASES setting.
        """
        collector = NestedObjects(using=using)
        collector.collect(objs)

        def format_callback(obj):
            return '%s: %s' % (capfirst(obj._meta.verbose_name), obj)

        to_delete = collector.nested(format_callback)
        protected = [format_callback(obj) for obj in collector.protected]
        model_count = {model._meta.verbose_name_plural: len(objs) for model, objs in collector.model_objs.items()}
        return to_delete, model_count, protected

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        obj = self.get_object()
        # Get a queryset so that we can get the database alias
        db_alias = self.model.objects.filter(pk=obj.pk).db
        to_delete, model_count, protected = self.get_deleted_objects([obj], db_alias)
        context.update({
            'object_name': self.model._meta.verbose_name,
            'objs_to_be_deleted': to_delete,
        })
        return context

更新：我覆盖了delete方法并首先删除了相关对象，但仍然收到IntegrityError。

我不确定这是否是解决问题的真正原因，但是当我第一次创建模型并迁移数据库时，我没有设置db_table名称，然后我更改了名称并已迁移但忘记删除默认名称的旧表。删除默认表并使用自定义数据库名称截断该表后，此问题已解决。

models.CASCADE在DeleteView中无法正常工作

0 个答案: