Django Rest Framework model Id field in nested relationship serializer

Question

I'm usign Django Rest Framework where I have the following two serializers:

class ServiceSerializer(serializers.ModelSerializer):     id = serializers.ReadOnlyField()      class Meta:         model = ServiceType         fields = ('id', 'serviceName', 'servicePrice')   class CompanyShortListSerializer(serializers.ModelSerializer):       services = ServiceSerializer(many=True)       class Meta:          model = Company          fields = ( 'id','name','address','cost_per_patient','cost_per_month','renting_fee','services') 

The ServiceType model looks like this:

class ServiceType(models.Model):      serviceName = EncryptedCharField(max_length=100, blank=True, verbose_name = "Typ usługi")      servicePrice = EncryptedFloatField(null=True, blank=True, verbose_name = "Cena usługi", validators = [MinValueValidator(0.1), MaxValueValidator(999)])      company = models.ForeignKey(Company, related_name = 'services') 

I would like to update the existing instances by changing the related services (e.g. deleting some of them). To achieve this I'm doing this:

def update(self, instance, validated_data):     # Updates an exisitng Company with several services      instance.name = validated_data['name']     instance.address = validated_data['address']     instance.cost_per_patient = validated_data['cost_per_patient']     instance.renting_fee = validated_data['renting_fee']     services_data = validated_data['services']      for item in services_data:         updatedService = ServiceType(             serviceName = item['serviceName'],             servicePrice = item['servicePrice'],             id=item['id'],              company=instance)         updatedService.save()      return instance 

The problem that I'm facing is that the service['id'] field is not provided - which means I get a KeyError 'id' - although I added it explicitly in the ServiceSerializer id field.

EDIT

Here's an exemplary request (taken from Chrome) that I'm posting:

 { "id":49,"name":"Test 1",    "address":"Testowa 1",    "renting_fee":200,    "cost_per_month":300,    "cost_per_patient":null,    "services":[    {"id":67,"serviceName":"Terapia","servicePrice":100},    {"id":68,"serviceName":"Terapia par","servicePrice":150},    {"id":69,"serviceName":"Terapia po angielsku","servicePrice":120}    ]  }  

What am I doing wrong and how to get the ID of a an object(basically ServiceSerializer) using nested serializers?

EDIT no.2

When I print from the serializer update function I get the following:

print(self.data['services']) gives me:

[  OrderedDict([('id', 67), ('serviceName', u'Terapia'), ('servicePrice', 100.0)]),  OrderedDict([('id', 68), ('serviceName', u'Terapia par'), ('servicePrice', 150.0)]),  OrderedDict([('id', 69), ('serviceName', u'Terapia po angielsku'), ('servicePrice', 120.0)]),   OrderedDict([('id', 70), ('serviceName', u'Terapia grupowa'), ('servicePrice', 140.0)]) ] 

However, print(services_data) gives the following (basically the same, but without the id):

[ OrderedDict([(u'serviceName', u'Terapia'), (u'servicePrice', 100.0)]), OrderedDict([(u'serviceName', u'Terapia par'), (u'servicePrice', 150.0)]), OrderedDict([(u'serviceName', u'Terapia po angielsku'), (u'servicePrice', 120.0)]) ] 

And the ids get lost ...

EDIT no.3

According to the Django Rest Framework docs If certain field will be shall be in the serializer output representation it should be a HiddenField. This however requires a default value ... I have checked that and indeed using this HiddenField with a default value 'solves' the problem - the ID is there in validated_data. The problem is that the id is not correct. Is there a possibility to set this id to the value of the object sent to the serializer?

Answer 1

Ok - I think I found the answer after ... carefully reading the docs :)

So according to the docs the id field could be set to a ModelField like this:

id = serializers.ModelField(model_field=ServiceType()._meta.get_field('id')) 

Indeed, after adding this line the id field is present in validated_data :)