的DRF无法发布通过主键的数据

Question

I'm starting to work with Django and I followed the tutorial available in the Django Rest Framework website and now I'm trying to adapt the tutorial to do something a little more complex.

I'm trying to create a "Like" system for a Social Network. A User can create Posts (UserPosts) and Like other user's posts.

I'm creating new UserPosts (using the command line) this way:

http -a admin:Pass1234 POST http://127.0.0.1:8000/posts/ description="I'm just a random comment"

And everything works just fine. The problem is when I try to create a Like instance. In this case I need to pass a UserPost id, so I'm doing the same as I did to create a new comment:

http -a admin:Pass1234 POST http://127.0.0.1:8000/likes/ post="1"

But when I do this I get the following error:

"post": {
        "non_field_errors": [
            "Invalid data. Expected a dictionary, but got unicode."
        ]
    }

The models are the following:

class UserPost(models.Model):
    owner = models.ForeignKey('auth.User', related_name='posts', on_delete=models.CASCADE)
    timestamp = models.DateTimeField(auto_now_add=True)
    description = models.CharField(max_length=100, blank=True, default='')

    def save(self, *args, **kwargs):
        options = self.description and {'description': self.description} or {}
        super(UserPost, self).save(*args, **kwargs)

    class Meta:
        ordering = ('timestamp',)


class Like(models.Model):
    owner = models.ForeignKey('auth.User', related_name='likes', on_delete=models.CASCADE)
    post = models.ForeignKey(UserPost, related_name='likes', on_delete=models.CASCADE)
    timestamp = models.DateTimeField(auto_now_add=True)

    def save(self, *args, **kwargs):
        options = self.post and {'post': self.post}
        super(Like, self).save(*args, **kwargs)

    class Meta:
        ordering = ('timestamp',)

The serializers:

class UserPostSerializer(serializers.HyperlinkedModelSerializer):
    owner = serializers.ReadOnlyField(source='owner.id')

    class Meta:
        model = UserPost
        fields = ('url', 'id', 'description', 'owner', 'timestamp')


class LikeSerializer(serializers.ModelSerializer):
    owner = serializers.ReadOnlyField(source='owner.id')
    post = UserPostSerializer(source='post')

    class Meta:
        model = Like
        fields = ('id', 'owner', 'post', 'timestamp')

The Views:

class PostViewSet(viewsets.ModelViewSet):
    queryset = UserPost.objects.all()
    serializer_class = UserPostSerializer
    permission_classes = (permissions.IsAuthenticatedOrReadOnly,
                          IsOwnerOrReadOnly,)

    def perform_create(self, serializer):
        serializer.save(owner=self.request.user)


class LikeViewSet(viewsets.ModelViewSet):
    queryset = Like.objects.all()
    serializer_class = LikeSerializer
    permission_classes = (permissions.IsAuthenticatedOrReadOnly, IsOwnerOrReadOnly,)

    def perform_create(self, serializer):
        serializer.save(owner=self.request.user)

Routers and urls:

router = DefaultRouter()
router.register(r'posts', views.PostViewSet)
router.register(r'users', views.UserViewSet)
router.register(r'likes', views.LikeViewSet)

urlpatterns = [
    url(r'^', include(router.urls)),
    url(r'^api-auth/', include('rest_framework.urls', namespace='rest_framework'))
]

Any idea of what is happening?

Thanks!

Answer 1

You need to remove post = UserPostSerializer from your LikeSerializer :

class LikeSerializer(serializers.ModelSerializer):
  owner = serializers.ReadOnlyField(source='owner.id')

  class Meta:
    model = Like
    fields = ('id', 'owner', 'post', 'timestamp')

so that django-rest-framework uses a PrimaryKeyRelatedField for the related UserPost (which is the default for related models with ModelSerializer).
Then you can create your Like entry with post="1" as parameter.