I have a frustrating problem with POST requests on a DRF serializer - DRF is, for some reason, going to an incorrect view name, and view_name is not a settable property on PrimaryKeyRelated Field.
Models:
# (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)
Serializers:
# (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__'
urls:
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')
I'm using the _id fields during POST and PUT to send the id's of the related obejcts, then serializing them. This worked great with AssessmentSerializer (and several others), but is failing for a reason that I can't figure out. Certainly, the appname is missing from the view returned in the error, but I don't know why that's happening, and why it didn't happen before.
Stack trace:
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
So, what I missed is that these are HyperlinkedModelSerializer. The difference with Assessment is how you handle the ManyToMany.
A HyperlinkedModelSerializer, generates HyperlinkedRelatedField for related fields and generates the view_name from rest_framework.utils.get_detail_view_name, which doesn't have a facility for an app name.
This is done by build_field, which delegates to build_relational_field based on model info obtained from rest_framework.utils.model_meta.get_field_info().
Your teacher field is probably in there.
I'm not certain why it works for Assessment as I can't find the condition that would reject/accept either, but my gut says that because PrimaryKeyRelatedField is a related field, it doesn't build a HyperlinkedRelatedField.
Either way, you should see what field name(s) is/are passed to build_relational_field to figure this out.
Remove the trailing comma after the field definition of teacher:
teacher = serializers.PrimaryKeyRelatedField(many=True, read_only=True),
------^
This turns teacher into a tuple and teachers_id disappears as well. As a result, the standard hyperlinked related field is created:
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')