Django Rest Framework Saying Non-Required Field Is Required

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The Backstory

In Django I have the models

class Company(models.Model):
    name = models.TextField(null=False,unique=True)
    date_added = models.DateTimeField(auto_now_add=True)

class Address(models.Model):
    street = models.TextField()

class Person(models.Model ): 
    firstname = models.TextField()
    address = models.ForeignKey(Address,null= True,on_delete=models.SET_NULL)
    company = models.ForeignKey(Company,null=True,on_delete=models.SET_NULL)

Where each person has an address and a company.(both non required fields)

In DRF I have the serializers.

class AddressSerializer(serializers.ModelSerializer):
    class Meta:
        model = Address
        fields = '__all__'

class CompanySerializer(serializers.ModelSerializer):

    class Meta:
        model = Company
        fields = "__all__"

class PersonSerializer(serializers.ModelSerializer):

    class Meta:
        model = Person
        fields = ('id', 'firstname',  'address','company')

    def to_representation(self, instance):
        response = super().to_representation(instance)
        response['address'] = AddressSerializer(instance.address).data
        response['company'] = CompanySerializer(instance.company).data
        return response

and the ViewSets

class PersonViewSet(viewsets.ModelViewSet,UpdateModelMixin):
    queryset = Person.objects.all()
    serializer_class = PersonSerializer
    filter_backends = (OrderingFilter,DjangoFilterBackend,SearchFilter)
    filter_fields = ('id','company','firstname','middlename','lastname',)
    search_fields = ('firstname','middlename','lastname',)

class CompanyViewSet(viewsets.ModelViewSet,UpdateModelMixin):
    queryset = Company.objects.all()
    serializer_class = CompanySerializer
    filter_backends = (OrderingFilter,DjangoFilterBackend,SearchFilter)
    filter_fields = ('id','name',)
    search_fields = ('name',)

class AddressViewSet(viewsets.ModelViewSet,UpdateModelMixin):
    queryset = Address.objects.all()
    serializer_class = AddressSerializer
    filter_backends = [DjangoFilterBackend]
    filter_fields = ['id','street']

The Issue

When posting the data {"firstname":"foo"} to this serializer, it returns a 400 error code saying. {"company": ["This field is required."]}.

The odd thing is, the address field is set up the seemingly exact same way as the company field but does not throw this error.

In order to make this work, you must post {"firstname":"foo","company":null} to the serializer, which seems a little silly considering that the address field works just fine.

Does anybody have any idea what would be causing this issue and how to prevent this from happening?

django python
3 Answers

You need to include blank=True in addition to null=True in your ForeignKey constructor, like this:

address = models.ForeignKey(Address,blank=True,null=True,on_delete=models.SET_NULL)
company = models.ForeignKey(Company,blank=True,null=True,on_delete=models.SET_NULL)
user_23997750

Not sure, but try changing it to this

fields = ('id', 'firstname',  'address','company',)
user_20423030

I simulated exactly what you have wrote but found no such problem as posted in the question. No error was thrown.

#My Models

class Company(models.Model):
    name = models.TextField(null=False,unique=True)
    date_added = models.DateTimeField(auto_now_add=True)

class Address(models.Model):
    street = models.TextField()

class Person(models.Model ):
    firstname = models.TextField()
    address = models.ForeignKey(Address,null= True,on_delete=models.SET_NULL)
    company = models.ForeignKey(Company,null=True,on_delete=models.SET_NULL)

#My Viewset

class PersonViewSet(viewsets.ModelViewSet, UpdateModelMixin):
    queryset = Person.objects.all()
    serializer_class = PersonSerializer
    filter_backends = (OrderingFilter, DjangoFilterBackend, SearchFilter)
    filter_fields = ('id', 'company', 'firstname', 'middlename', 'lastname',)
    search_fields = ('firstname', 'middlename', 'lastname',)


class CompanyViewSet(viewsets.ModelViewSet, UpdateModelMixin):
    queryset = Company.objects.all()
    serializer_class = CompanySerializer
    filter_backends = (OrderingFilter, DjangoFilterBackend, SearchFilter)
    filter_fields = ('id', 'name',)
    search_fields = ('name',)


class AddressViewSet(viewsets.ModelViewSet, UpdateModelMixin):
    queryset = Address.objects.all()
    serializer_class = AddressSerializer
    filter_backends = [DjangoFilterBackend]
    filter_fields = ['id', 'street']

#My Serializer

class AddressSerializer(serializers.ModelSerializer):
    class Meta:
        model = Address
        fields = '__all__'

class CompanySerializer(serializers.ModelSerializer):

    class Meta:
        model = Company
        fields = "__all__"

class PersonSerializer(serializers.ModelSerializer):

    class Meta:
        model = Person
        fields = ('id', 'firstname',  'address','company')

    def to_representation(self, instance):
        response = super().to_representation(instance)
        response['address'] = AddressSerializer(instance.address).data
        response['company'] = CompanySerializer(instance.company).data
        return response

#My tests
class PersonTests(APITestCase):

    def test_create_person(self):
        url = reverse('person-list')
        data = {"firstname": "foo"}
        response = self.client.post(url, data, format='json')
        print(response.content)
        self.assertEqual(response.status_code, HTTP_201_CREATED)

Test Results:

user_57705600
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