DoesNotExist -- 匹配查询错误

Question

我正在尝试按类别列出一组交易

我有一个交易模型和一个类别模型，其中类别是交易的外键，如下所示：

class Deal(models.Model):
    title = models.CharField(max_length=200)
    slug = models.SlugField(max_length=140, unique=True)
    description = models.TextField(default='')
    category = models.ForeignKey(Category)

类别页面的 urlpattern 如下所示：

url(r'^category/(?P<category>\w+)/$', deals_by_category, name='category')

其他网址如下所示：

    url(r'^all/$', DealListView.as_view(), name='deals'),
    url(r'^(?P<slug>.*)/$', deal_by_detail, name='deal_detail'),
    url(r'^category/(?P<category>\w+)/$', deals_by_category, name='category'),
    url(r'^home/$', DealHome.as_view(), name='deal_home'),
    url(r'^test/$', Home.as_view(), name='deal_test'),
    url(r'^(?P<pk>[0-9]+)/like', like, name='like'),

这个 urlpattern 的视图是这样的：

def deals_by_category(request,category):
    category_deals = Deal.objects.filter(category__name=category,
                                           )
    return render(request, 'deals/category.html', {'category_deals': category_deals})

我的其他视图如下所示：

class DealListView(generic.ListView):
    model = Deal
    context_object_name = 'deal_list'
    queryset = Deal.objects.all()
    template_name = 'deal_list.html'

 class DealHome(generic.TemplateView):
    model = Deal
    template_name = 'deals/test.html

def deal_by_detail(request, slug):
    deal_detail = Deal.objects.get(slug=slug)
    return render(request, 'deals/deal_detail.html', {'deal_detail': deal_detail})

def like(request, pk):
    if request.method == 'POST':
        deal = Deal.objects.get(pk=pk)
        deal.likes_total += 1
        deal.save()
        return redirect('home')

然后我的 category.html 模板会像这样循环遍历这些返回的交易：

{% for deal in category_deals %}
 <h5 class="card-retailer">{{ deal.retailer}}</h5>
                <p class="card-title">{{ deal.title }}</p>

现在如果我点击这样的预定类别链接就会出现问题：

http://localhost:8000/deals/category/Apparel/

但错误不是指向我的“deals_by_category”视图，而是指向每个交易的单个视图 --- 堆栈跟踪指向下面的第二行。我认为这一定很容易解决，但过去几个小时一直盯着这个问题，无法确定问题所在。

def deal_by_detail(request, slug):
    deal_detail = Deal.objects.get(slug=slug)
    return render(request, 'deals/deal_detail.html', {'deal_detail': deal_detail})

注意这里是完整的错误和回溯：

DoesNotExist at /deals/category/Apparel/
Deal matching query does not exist.
Request Method: GET
Request URL:    http://localhost:8000/deals/category/Apparel/

追溯：

File "C:\Users\crstu\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\core\handlers\base.py" in get_response
  149.                     response = self.process_exception_by_middleware(e, request)

File "C:\Users\crstu\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\core\handlers\base.py" in get_response
  147.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "C:\Users\crstu\Desktop\JSPROJ\dealmazing\deals\views.py" in deal_by_detail
  22.     deal_detail = Deal.objects.get(slug=slug)

File "C:\Users\crstu\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\db\models\manager.py" in manager_method
  122.                 return getattr(self.get_queryset(), name)(*args, **kwargs)

File "C:\Users\crstu\AppData\Local\Programs\Python\Python36-32\lib\site-packages\django\db\models\query.py" in get
  387.                 self.model._meta.object_name

Exception Type: DoesNotExist at /deals/category/Apparel/
Exception Value: Deal matching query does not exist.

Answer 1

您的deal_by_detail URL 模式可以捕获任何字符序列。所以它将匹配任何 URL；它下面的任何其他模式都不会被调用。

您应该更具体，就像您对 category 模式所做的那样。

url(r'^(?P<slug>\w+)/$', deal_by_detail, name='deal_detail'),

Answer 2

正如堆栈跟踪所指出的，这就是问题所在。

deal_detail = Deal.objects.get(slug=slug)

当使用get且对象不存在时会出现异常DoesNotExist。这意味着您尝试使用的 slug 在数据库中不存在。

当您想要获取类别视图而不是详细视图时，错误实际上在于正则表达式（正如您正确怀疑的那样）。错误在于您使用了.*，这是贪婪的并且使用了所有剩余的字符。

如果您改为将正则表达式更改为以下内容。 r'^s/(?P<slug>\w+)/$'，请注意开头的 s，这有助于保持 url 与其他 url 不同以及仅使用字母数字字符的 \w+。