get_url(): AttributeError: 'OrderedDict' object has no attribute 'pk'

[ghost]

Testing code:

class UserViewSet(viewsets.ModelViewSet):
    queryset = get_user_model().objects.all()
    serializer_class = UserSerializer
    permission_classes = (permissions.IsAdminUser,)

    def perform_create(self, serializer):
        email = serializer.data['email']
        password = serializer.data['password']
        extra_fields = {}
        if 'is_staff' in serializer.data:
            extra_fields['is_staff'] = serializer.data['is_staff']
        if 'is_active' in serializer.data:
            extra_fields['is_active'] = serializer.data['is_active']
        get_user_model().objects.create_user(email, password, **extra_fields)

Error:

[05/Mar/2015 03:09:44] ERROR [base:231] Internal Server Error: /api/users/
Traceback (most recent call last):
  File "/env/lib/python2.7/site-packages/django/core/handlers/base.py", line 111, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/env/lib/python2.7/site-packages/django/views/decorators/csrf.py", line 57, in wrapped_view
    return view_func(*args, **kwargs)
  File "/env/src/djangorestframework/rest_framework/viewsets.py", line 85, in view
    return self.dispatch(request, *args, **kwargs)
  File "/env/src/djangorestframework/rest_framework/views.py", line 452, in dispatch
    response = self.handle_exception(exc)
  File "/env/src/djangorestframework/rest_framework/views.py", line 449, in dispatch
    response = handler(request, *args, **kwargs)
  File "/env/src/djangorestframework/rest_framework/mixins.py", line 20, in create
    self.perform_create(serializer)
  File "/api/views.py", line 29, in perform_create
    email = serializer.data['email']
  File "/env/src/djangorestframework/rest_framework/serializers.py", line 466, in data
    ret = super(Serializer, self).data
  File "/env/src/djangorestframework/rest_framework/serializers.py", line 215, in data
    self._data = self.to_representation(self.validated_data)
  File "/env/src/djangorestframework/rest_framework/serializers.py", line 435, in to_representation
    ret[field.field_name] = field.to_representation(attribute)
  File "/env/src/djangorestframework/rest_framework/relations.py", line 267, in to_representation
    return self.get_url(value, self.view_name, request, format)
  File "/env/src/djangorestframework/rest_framework/relations.py", line 202, in get_url
    if obj.pk is None:
AttributeError: 'OrderedDict' object has no attribute 'pk'
[05/Mar/2015 03:09:44] "POST /api/users/ HTTP/1.1" 500 120552

Root cause: there's no pk in the OrderedDict yet at that time.

[jpadilla]

@zhigang you should really be calling serializer.save() or better yet a custom create() on your serializer. There are a couple of examples in the Serializers docs.

[ghost]

@jpadilla : thanks and I think you are right I should override the serializer create() method to do this.

But it seems the issue alone needs a code fix. Let's keep it open for now.

[tomchristie]

Can we reduce this to a more minimal example?

[ghost]

Code to reproduce it:

views.py:

from django.contrib.auth import get_user_model

from rest_framework import permissions, serializers, viewsets


class UserSerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = get_user_model()
        fields = ('url', 'id', 'username', 'email', 'password', 'is_active', 'is_staff', 'is_superuser', 'date_joined', 'last_login')


class UserViewSet(viewsets.ModelViewSet):
    queryset = get_user_model().objects.all()
    serializer_class = UserSerializer
    permission_classes = (permissions.IsAdminUser,)

    def perform_create(self, serializer):
        username = serializer.data['username']
        email = serializer.data['email']
        password = serializer.data['password']
        extra_fields = {}
        if 'is_staff' in serializer.data:
            extra_fields['is_staff'] = serializer.data['is_staff']
        if 'is_active' in serializer.data:
            extra_fields['is_active'] = serializer.data['is_active']
        get_user_model().objects.create_user(username, email, password, **extra_fields)

urls.py:

from django.conf.urls import patterns, include, url
from django.contrib import admin

from rest_framework import routers

from views import UserViewSet


router = routers.DefaultRouter()
router.register('users', UserViewSet)


urlpatterns = patterns('',
    url(r'^api/', include(router.urls)),
    url(r'^api/api-auth/', include('rest_framework.urls', namespace='rest_framework')),
    url(r'^admin/', include(admin.site.urls)),
)

POST to http://127.0.0.1:8000/api/users/

Patch to fix this: #2641

[carltongibson]

OK. I've had a play with this in the shell. This comes up if you call data without save on a HyperlinedModelSerializer containing a url field.

1. With the recommended behaviour, calling save or create on your serializer (as per @jpadilla's first comment here) you're never going to see this.
2. If there's a legitimate reason not to do that you can access validated_data in your custom perform_create.

On this basis I'm going to close this as wrong usage.

(Mis-using data seems a common issue with the move to 3.0 — probably because all the older examples used it. A more prominent discussion of the various properties here may be worthwhile.)

[carltongibson]

Having looked back at #2637 I have a slight niggle about whether there's some example where you might legitimately want to call data and a HyperlinedModelSerializer containing a url field to serialise an unsaved object.

My first thought there is "Just remove the field" — i.e. it's an edge-case that the user can handle easily themselves — but if anybody wants to drop a failing test case in here we can look at re-opening again.

[ghost]

What if we just merge #2641 ? Is that better than just saying: don't do it?

[flamingofugang]

I faced the same issue when I try to upload an image file to the DRF REST interface.

There is no problem when I use 'curl -X POST'. However, when I use angularjs http post service (ajax call), I got the same error message, said function 'get_url()' raised 'obj.pk is none' error.

Here is the models.py

def upload_to(instance, filename):
    return 'post_image/{0}/{1}'.format(instance.author.id, filename)

class PostImage(models.Model):
    author = models.ForeignKey(Author, blank=False, editable=False, related_name='images')
    post = models.ForeignKey(Post, blank=False, editable=False, related_name='images')

    image = models.ImageField(_('image'), blank=True, null=True, upload_to=upload_to)
    created = models.DateTimeField(editable=False)
    updated = models.DateTimeField(editable=False)

    def __unicode__(self):
        return self.name

    def save(self, *args, **kwargs):
        ''' On save, update timestamps '''
        if not self.id:
            self.created = timezone.now()
        self.updated = timezone.now()
        return super(PostImage, self).save(*args, **kwargs)

Here is the serializers.py

class PostImageSerializer(serializers.HyperlinkedModelSerializer):
    author = serializers.HyperlinkedRelatedField(read_only=True, view_name='author-detail')
    post = serializers.HyperlinkedRelatedField(read_only=True, view_name='post-detail')

    class Meta:
        model = PostImage
        fields = ('url', 'image', 'author', 'post', 'created', 'updated')

Here is the views.py

class PostImageView(generics.ListCreateAPIView):
    """
    List and Create post image endpoint
    Allowed request method: Get, Post
    """
    serializer_class = PostImageSerializer
    permission_classes = [permissions.IsAuthenticated]
    parser_classes = (FormParser, MultiPartParser, FileUploadParser,)

    def get_queryset(self):
        queryset = super(PostImageView, self).get_queryset()
        return queryset.filter(post__pk=self.kwargs['pk'])

    def perform_create(self, serializer):
        post = Post.objects.get(pk=self.kwargs['pk'])
        if 'upload' in self.request.data:
            file_obj = self.request.data['upload']
            serializer.save(author=self.request.user, post=post, image=file_obj)
            return Response(status=status.HTTP_201_CREATED)
        else:
            return Response(status=status.HTTP_400_BAD_REQUEST)

[xordoquy]

Unless we have a failing test case that demonstrate the error is on DRF side, there isn't much we can do.
Also note that perform_create shouldn't return anything (see rest_framework/mixins.py)

[allardbrain]

Having looked back at #2637 I have a slight niggle about whether there's some example where you might legitimately want to call data and a HyperlinedModelSerializer containing a url field to serialise an unsaved object.

My first thought there is "Just remove the field" — i.e. it's an edge-case that the user can handle easily themselves — but if anybody wants to drop a failing test case in here we can look at re-opening again.

All these years later, this proved to me massively helpful! Thanks so much. You ended a 2-hour rabbit hole I just spent trying to resolve this.