Django 2.1 create method to create nested fields (foreignkey relation). Using Django's Rest Framework

Question

Which method should I use in jango 2.1 for the create method to add new objects that supports also the creation of nested fields (ForeignKey relation). I always get the Error Message:

AssertionError at /client/create/ The .create() method does not support writable nested fields by default.

User Model

class User(models.Model):
gender = models.CharField(max_length=10, choices=GENDER)
first_name = models.CharField(max_length=20)
last_name = models.CharField(max_length=20)
position = models.CharField(max_length=50)
birthday = models.DateField(auto_created=False)
email = models.EmailField(max_length=50)
phone = models.CharField(max_length=15)
password = models.CharField(max_length=100)

def __str__(self):
    return f"{self.first_name} {self.last_name} {self.position} {self.email} {self.phone} {self.password}"

Company Model

class Company(models.Model):
company_name = models.CharField(max_length=50, blank=False)
address = models.CharField(max_length=50, blank=False)
zip = models.IntegerField(blank=False)
city = models.CharField(max_length=50, blank=False)
email = models.EmailField(max_length=50, blank=False)

def __str__(self):
    return f"{self.company_name} {self.address} {self.zip} {self.city}"

Client Company

class ClientCompany(models.Model):
client = models.ForeignKey(Company, on_delete=models.PROTECT)
contact_person = models.ForeignKey(User, on_delete=models.PROTECT)
status = models.CharField(max_length=15, choices=STATUS, default='Aktiv')

def __str__(self):
    return f"{self.client} {self.contact_person} {self.status}"

User Serializer

class UserSerializer(serializers.ModelSerializer):
class Meta:
    model = User
    fields = '__all__'

ClientCompanySerializer

class ClientCompanySerializer(serializers.ModelSerializer):
    client = CompanySerializer(many=False, read_only=False)
    contact_person = ClientUserSerializer(many=False, read_only=True)

    class Meta:
        model = ClientCompany
        fields = '__all__'

UserUrls

    urlpatterns = [
path('update/id<int:id>', UpdateUserByID.as_view(), name='user-update'),
path('id/<int:id>', GetUserByID.as_view(), name='user-id'),
path('create', CreateUser.as_view(), name='create-user'),
path('delete/id/<int:id>', DeleteUserByID.as_view(), name='delete-user'),

]

CompanyUrls

urlpatterns = [
path('update/id<int:id>', CompanyUpdateByID.as_view(), name='company-udpate'),
path('id/<int:id>', CompanyById.as_view(), name='company-id'),
path('create/', CreateCompany.as_view(), name='company-create'),
path('delete/id/<int:id>', DeleteCompanyByID.as_view(), name='company-delete')

]

CompanyView

class CreateCompany(generics.CreateAPIView):
queryset = Company.objects.all()
serializer_class = CompanySerializer

My goal is to create a new company (and the related fk 'contact_person') in the url /company/create/

Is there a way to create the related 'contact_person' within the 'ClientCompanySerializer' or should I use a different approach.

Please, share your models and serializers for Company and User. — HuLu ViCa
– HuLu ViCa, Commented Feb 13, 2019 at 14:25
Hi Hugo, I have added the company and user serializer + model, thank you! — Jetmir
– Jetmir, Commented Feb 13, 2019 at 15:08
How are you sending the data for contact_person? I think I am going to need your urls.py and your related views too. — HuLu ViCa
– HuLu ViCa, Commented Feb 13, 2019 at 15:13

Ashwin Bande · Accepted Answer · 2019-02-13 16:07:56Z

1

you need to override the default create and update methods in serializers like below:

first remove read_only=True from contact_person

def create(self, validated_data):
client = validated_data.pop('client')
contact_person = validated_data.pop('contact_person')
client_instance = Company.object.create(**client)
contact_person_instance = User.object.create(**contact_person)
return ClientCompany.objects.create(client=client_instance,contact_person=contact_person_instance , **validated_data)

also, implement a similar method for update

edited Feb 13, 2019 at 16:07

answered Feb 13, 2019 at 15:37

Ashwin Bande

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2 Comments

Jetmir Over a year ago

Thanks a lot, it's working properly fine as it is supposed to! :)

Ashwin Bande Over a year ago

@Jetmir please mark the answer as accepted, so that others can also be sure that it is a working solution.

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