DRF 无法使用 PrimaryKeyRelatedField 上的视图名称解析超链接关系的 URL

Posted 2023-02-24

【中文标题】DRF 无法使用 PrimaryKeyRelatedField 上的视图名称解析超链接关系的 URL

【英文标题】：DRF Could not resolve URL for hyperlinked relationship using view name on PrimaryKeyRelatedField

【发布时间】：2021-04-03 01:00:51

【问题描述】：

我对 DRF 序列化程序上的 POST 请求有一个令人沮丧的问题 - 由于某种原因，DRF 转到了不正确的视图名称，并且view_name 不是PrimaryKeyRelated Field 上的可设置属性。

型号：

# (the class with the issue)
class Section(models.Model):
    teacher = models.ManyToManyField(Teacher)

# (a class that works, using the same pattern)
class Assessment(models.Model):
    standards = models.ManyToManyField(Standard)

序列化器：

# (doesn't work)
class SectionInfoSerializer(serializers.HyperlinkedModelSerializer):
    url = serializers.HyperlinkedIdentityField(view_name="gbook:section-detail")
    teacher = serializers.PrimaryKeyRelatedField(many=True, read_only=True),
    teachers_id = serializers.PrimaryKeyRelatedField(write_only=True, queryset=Teacher.objects.all(), many=True, source='teacher', allow_empty=False)

    class Meta:
        model = Section
        fields = '__all__'
        read_only_fields = ['sendEmails', 'teacher', 'course']

# (works)
class AssessmentSerializer(serializers.HyperlinkedModelSerializer):
    pk = serializers.PrimaryKeyRelatedField(read_only=True)
    url = serializers.HyperlinkedIdentityField(view_name="appname:assessments-detail")
    standards = serializers.PrimaryKeyRelatedField(read_only=True, many=True)
    standards_id = serializers.PrimaryKeyRelatedField(queryset=Standard.objects.all(), source='standards', write_only=True, many=True, allow_empty=False)

    class Meta:
        model = Assessment
        fields = '__all__'

网址：

router.register(r'teachers', teacher_views.TeacherViewSet, basename='teacher')
router.register(r'sections', course_views.SectionViewSet)
router.register(r'standards', gbook.views.standard_views.StandardViewSet, basename='standards')
router.register(r'assessments', AssessmentViewSet, basename='assessments')

我在 POST 和 PUT 期间使用_id 字段来发送相关对象的 id，然后对其进行序列化。这对AssessmentSerializer（和其他几个）非常有效，但由于我无法弄清楚的原因而失败。当然，错误中返回的视图中缺少 appname，但我不知道为什么会发生这种情况，以及为什么以前没有发生过。

堆栈跟踪：

Internal Server Error: /appname/sections/
Traceback (most recent call last):
  File "/venv2/lib/python3.8/site-packages/rest_framework/relations.py", line 393, in to_representation
    url = self.get_url(value, self.view_name, request, format)
  File "/venv2/lib/python3.8/site-packages/rest_framework/relations.py", line 331, in get_url
    return self.reverse(view_name, kwargs=kwargs, request=request, format=format)
  File "/venv2/lib/python3.8/site-packages/rest_framework/reverse.py", line 47, in reverse
    url = _reverse(viewname, args, kwargs, request, format, **extra)
  File "/venv2/lib/python3.8/site-packages/rest_framework/reverse.py", line 60, in _reverse
    url = django_reverse(viewname, args=args, kwargs=kwargs, **extra)
  File "/venv2/lib/python3.8/site-packages/django/urls/base.py", line 87, in reverse
    return iri_to_uri(resolver._reverse_with_prefix(view, prefix, *args, **kwargs))
  File "/venv2/lib/python3.8/site-packages/django/urls/resolvers.py", line 685, in _reverse_with_prefix
    raise NoReverseMatch(msg)
django.urls.exceptions.NoReverseMatch: Reverse for 'teacher-detail' not found. 'teacher-detail' is not a valid view function or pattern name.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/lib/python3.8/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/lib/python3.8/site-packages/django/core/handlers/base.py", line 179, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/lib/python3.8/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/lib/python3.8/site-packages/rest_framework/viewsets.py", line 114, in view
    return self.dispatch(request, *args, **kwargs)
  File "/lib/python3.8/site-packages/rest_framework/views.py", line 505, in dispatch
    response = self.handle_exception(exc)
  File "/lib/python3.8/site-packages/rest_framework/views.py", line 465, in handle_exception
    self.raise_uncaught_exception(exc)
  File "/lib/python3.8/site-packages/rest_framework/views.py", line 476, in raise_uncaught_exception
    raise exc
  File "/lib/python3.8/site-packages/rest_framework/views.py", line 502, in dispatch
    response = handler(request, *args, **kwargs)
  File "/lib/python3.8/site-packages/rest_framework/mixins.py", line 20, in create
    headers = self.get_success_headers(serializer.data)
  File "/lib/python3.8/site-packages/rest_framework/serializers.py", line 562, in data
    ret = super().data
  File "/lib/python3.8/site-packages/rest_framework/serializers.py", line 260, in data
    self._data = self.to_representation(self.instance)
  File "/lib/python3.8/site-packages/rest_framework/serializers.py", line 529, in to_representation
    ret[field.field_name] = field.to_representation(attribute)
  File "/lib/python3.8/site-packages/rest_framework/relations.py", line 533, in to_representation
    return [
  File "/lib/python3.8/site-packages/rest_framework/relations.py", line 534, in <listcomp>
    self.child_relation.to_representation(value)
  File "/lib/python3.8/site-packages/rest_framework/relations.py", line 408, in to_representation
    raise ImproperlyConfigured(msg % self.view_name)
django.core.exceptions.ImproperlyConfigured: Could not resolve URL for hyperlinked relationship using view name "teacher-detail". You may have failed to include the related model in your API, or incorrectly configured the `lookup_field` attribute on this field.
[24/Dec/2020 09:55:04] "POST /appname/sections/ HTTP/1.1" 500 157269

【问题讨论】：

我几乎可以肯定您没有名为 teacher-detail 的视图/网址，但可能是 @987654332 @。您可以使用this method 列出项目中的所有 URL 模式，并使用 grep 表达式查看实际的 URL 名称是什么

正确 - teacher-detail 不是视图：应该是 appname:teacher-detail。但是，没有办法在我知道的那个字段上设置正确的视图名称

有一个teachers_id（复数），但有一个teacher 字段（单数）。复制/粘贴错误还是真正的问题？

您可以使用HyperlinkedRelatedField 和view_name 参数@DeltaG

@JPG PrimaryKeyRelatedField 没有理由需要视图。那就是问题所在。它应该只是将 id 粘贴在数据库字段中。

【参考方案1】：

所以，我错过的是这些是 HyperlinkedModelSerializer。评估的不同之处在于您如何处理多对多。

HyperlinkedModelSerializer，为相关字段生成 HyperlinkedRelatedField 并从 rest_framework.utils.get_detail_view_name 生成 view_name，它没有应用程序名称的功能。

这是由build_field 完成的，它根据从rest_framework.utils.model_meta.get_field_info() 获得的模型信息委托给build_relational_field。

您的teacher 字段可能在其中。

我不确定为什么它适用于评估，因为我也找不到拒绝/接受的条件，但我的直觉说，因为 PrimaryKeyRelatedField 是一个相关字段，它不会构建 HyperlinkedRelatedField。

无论哪种方式，您都应该查看传递给 build_relational_field 的字段名称以弄清楚这一点。

解决方案

去掉teacher字段定义后面的逗号：

teacher = serializers.PrimaryKeyRelatedField(many=True, read_only=True),
                                                                 ------^

这会将教师变成一个元组，并且教师 ID 也会消失。结果，创建了标准的超链接相关字段：

SectionInfoSerializer(instance=<Section: Section object (1)>):
    url = HyperlinkedIdentityField(view_name='gbook:section-detail')
    teachers_id = PrimaryKeyRelatedField(allow_empty=False, many=True, queryset=<QuerySet [<Teacher: Teacher object (1)>]>, source='teacher', write_only=True)
    send_emails = BooleanField(required=False)
    teacher = HyperlinkedRelatedField(allow_empty=False, many=True, read_only=True, view_name='teacher-detail')
    course = HyperlinkedRelatedField(allow_empty=False, many=True, read_only=True, view_name='course-detail')

【讨论】：

Course 没有老师。没有一个相关模型有任何包含Teacher的相关对象，并且teacher-detail（前面没有appname）在项目的任何地方都不存在

已更新。希望这能让你到达那里，但如果不逐步了解，很难看出真正的罪魁祸首在哪里。

感谢您的线索 - 我正在追踪它。值得注意的是，如果teacher 是PrimaryKeyRelatedField，这仍然不起作用。

看起来build_relational_field 没有为此字段调用。我在调试器处理 course_id 时受到了打击（另一个以完全相同的方式构建的字段），但在正确工作的评估序列化程序中，standards_id 却没有

这是一个绝妙的收获！我还能够通过修改模型中的字段来解决它，但逗号仍然存在：teachers = models.ManyToManyField(Teacher, db_table='gbook_section_teacher') ...但逗号确实是解决它的一种简单方法。谢谢！