Django 'When' 对象不可迭代

Question

我正在使用 django-filter 来显示员工的工作时间。

models.py：

    ...
    class Attendance(models.Model):
        user = models.ForeignKey(User, on_delete=models.CASCADE, related_name="Attendances")
        day = models.DateField()
        start_time = models.TimeField()
        end_time = models.TimeField()
        is_confirmed = models.BooleanField()
        task = models.ForeignKey(Tasks, on_delete=models.CASCADE)
        
     class Task(models.Model):
        title = models.CharField(max_length=255)
        project = models.ForeignKey(Project, on_delete=models.CASCADE, related_name="Tasks")
        assignee = models.ForeignKey(User, on_delete=models.CASCADE)
       
    ...

过滤器.py：

class WorkhourFilter(django_filters.FilterSet):
    user = django_filters.ModelChoiceFilter(queryset=User.objects.filter(is_superuser=False),field_name="user")
    project = django_filters.ModelChoiceFilter(queryset=Project.objects.all(), field_name="task__project")
    year = django_filters.ChoiceFilter(choices=tuple((x, x) for x in settings.YEARS_LIST),method='year_search')
    month = django_filters.ChoiceFilter(choices=tuple((i, x) for i, x in enumerate(settings.MONTH_LIST)),method='month_search' )
    
    class Meta:
    model = Attendance
    fields = ['user']
        
    def __init__(self, *args, **kwargs):
         super(WorkhourFilter, self).__init__(*args, **kwargs)
         start_date = ...
         end_date = ...
         self.queryset = self.Meta.model.objects.filter(user=self.request.user, 
         day__gte=start_date, day__lte=end_date).values('task__project__title', 
         'task__project').annotate(
          raw_work_hour=Sum(F('end_time') - F('start_time'), ),
          confirmed_work_hour=Sum(Case(When(is_verified=1, 
          then=F('end_time') - 
          F('start_time'))))).order_by('task__project')

我收到

'When' object is not iterable

错误。

confirmed_work_hour

有问题，但

raw_work_hour

本身不是问题。

此查询在相应视图的

get_queryset()

中运行良好，但当我尝试应用过滤器时，它会中断。

踪迹：

Django Version: 4.2.5
Python Version: 3.9.13
Installed Applications:
['django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'django_extensions',
 'crispy_forms',
 'crispy_bootstrap5',
 'django_tables2',
 'django_htmx',
 'django_filters',
 'ckeditor',
 'ckeditor_uploader',
 'guardian',
 'django_cascading_dropdown_widget',
 'dashboard.apps.DashboardsConfig',
 'auth.apps.AuthConfig']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware',
 'django_htmx.middleware.HtmxMiddleware']



Traceback (most recent call last):
  File "D:\Python\DjangoTest\venv\lib\site-packages\django\core\handlers\exception.py", line 55, in inner
    response = get_response(request)
  File "D:\Python\DjangoTest\venv\lib\site-packages\django\core\handlers\base.py", line 197, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "D:\Python\DjangoTest\venv\lib\site-packages\django\views\generic\base.py", line 104, in view
    return self.dispatch(request, *args, **kwargs)
  File "D:\Python\DjangoTest\venv\lib\site-packages\django\contrib\auth\mixins.py", line 73, in dispatch
    return super().dispatch(request, *args, **kwargs)
  File "D:\Python\DjangoTest\venv\lib\site-packages\braces\views\_access.py", line 438, in dispatch
    return super(StaffuserRequiredMixin, self).dispatch(
  File "D:\Python\DjangoTest\venv\lib\site-packages\braces\views\_access.py", line 375, in dispatch
    return super(GroupRequiredMixin, self).dispatch(
  File "D:\Python\DjangoTest\venv\lib\site-packages\django\views\generic\base.py", line 143, in dispatch
    return handler(request, *args, **kwargs)
  File "D:\Python\DjangoTest\venv\lib\site-packages\django_filters\views.py", line 74, in get
    self.filterset = self.get_filterset(filterset_class)
  File "D:\Python\DjangoTest\venv\lib\site-packages\django_filters\views.py", line 38, in get_filterset
    return filterset_class(**kwargs)
  File "D:\Python\DjangoTest\dashboard\filters\workhour_project.py", line 71, in __init__
    confirmed_work_hour=Sum(Case(When(is_verified=1, then=F('end_time') - F('start_time')))),
  File "D:\Python\DjangoTest\venv\lib\site-packages\sqlparse\sql.py", line 160, in __init__
    [setattr(token, 'parent', self) for token in self.tokens]

Exception Type: TypeError at /report/workhour/by_project
Exception Value: 'When' object is not iterable

Answer 1

问题不在

When

中，问题是 -

Case(When

被

Count

包裹着。

在您的案例中，解决方案是将 Case(When 和 Count 分成两个

annottate(

声明。