DoesNotExist - 匹配的查询不存在

Question

我有这个基于 django 类的视图，我试图覆盖 get_queryset 函数，因为我想从前端获取插入的值，以便在具有该名称的主题之后在我的数据库中搜索，然后获取 id。但是当我调用视图时，它给了我一个“主题匹配查询不存在”。因为 subject_val 是无。这是有道理的，因为用户尚未提交值 jet.. 那么我如何让它等到用户选择“提交”

class AttendanceList(LoginRequiredMixin, ListView):
    model = AttendanceLog
    template_name = "./attendancecode/showattendance.html"


    def get_queryset(self):
       class_val = self.request.GET.get('class')
       subject_val = self.request.GET.get('subject')
       sub = Subject.objects.get(name=subject_val).id
       new_context = get_statstic(class_val, sub)
       return new_context

    def get_context_data(self, **kwargs):
        context = super(AttendanceList, self).get_context_data(**kwargs)
        context['class'] = self.request.GET.get('class')
        context['subject'] = self.request.GET.get('subject')
        return context

Answer 1

您可以检查这些值是否不是None，如果是，则需要返回另一个AttendanceLogs 的查询集（例如AttendanceLog.objects.all() 或AttendanceLog.objects.none()）：

class AttendanceList(LoginRequiredMixin, ListView):
    model = AttendanceLog
    template_name = "./attendancecode/showattendance.html"

    def get_queryset(self):
       class_val = self.request.GET.get('class')
       subject_val = self.request.GET.get('subject')
       if class_val is not None and subject_val is not None:
           sub = Subject.objects.get(name=subject_val).id
           return get_statstic(class_val, sub)
       # return another queryset:
       return AttendanceLog.objects.none()

    # …