问题
when I try to create a new Post by posting the following JSON:
{
"text": "test",
"location": 1
}
I get the following error:
NOT NULL constraint failed: grapevineapp_post.location_id
models.py:
class Location(models.Model):
name = models.CharField(max_length=80)
created = models.DateTimeField(auto_now_add=True)
def __str__(self):
return self.name
class Post(models.Model):
text = models.CharField(max_length=512)
owner = models.ForeignKey('auth.User', related_name='posts', on_delete=models.CASCADE)
location = models.ForeignKey(Location, related_name='posts', on_delete=models.CASCADE)
created = models.DateTimeField(auto_now_add=True)
def __str__(self):
return self.text
views.py:
class PostList(generics.ListCreateAPIView):
permission_classes = (permissions.IsAuthenticatedOrReadOnly,)
queryset = Post.objects.all()
serializer_class = PostSerializer
def perform_create(self, serializer):
serializer.save(owner=self.request.user)
class PostDetail(generics.RetrieveUpdateDestroyAPIView):
permission_classes = (permissions.IsAuthenticatedOrReadOnly,)
queryset = Post.objects.all()
serializer_class = PostSerializer
Serializers.py
class PostSerializer(serializers.Serializer):
id = serializers.IntegerField(read_only=True)
text = serializers.CharField(required=False, allow_blank=True, max_length=512)
owner = serializers.ReadOnlyField(source='owner.username')
location = serializers.PrimaryKeyRelatedField(many=False, read_only=True)
def create(self, validated_data):
return Post.objects.create(**validated_data)
def update(self, instance, validated_data):
instance.text = validated_data.get('text', instance.text)
instance.location = validated_data.get('location', instance.location)
instance.save()
return instance
class UserSerializer(serializers.ModelSerializer):
posts = serializers.PrimaryKeyRelatedField(many=True, queryset=Post.objects.all())
class Meta:
model = User
fields = ('id', 'username', 'posts')
DB has already been cleared. Locations have been created by using the admin interface. I know that the issue is something trivial, but I just can't get it to work.
回答1:
To elaborate on what Willem Van Onsem said, you have your PostSerializer.location
field set as read-only
. The json data that you provided for it will be ignored (documentation), i.e. it won't be included in your validated_data
.
Then when you call Post.objects.create(**validated_data)
in your create
method it tries to create an instance of Post
without the location argument and you get your error.
EDIT: After your comment above about queryset.
You need to provide a queryset for it to validate against (documentation). In your case you want
location = serializers.PrimaryKeyRelatedField(
many=False,
queryset=Location.objects.all()
)
来源:https://stackoverflow.com/questions/53687071/django-rest-framework-not-null-constraint-failed