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?

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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 :)

Django Rest Framework model Id field in nested relationship serializer

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