How to POST Model with Many to Many through in Django REST - django

Question

I have a model with a many to many connection. I would like to make this model available in Django REST. By default such a model is read only, but I would also like to write. Furthermore, it would be great to get the information of the through connection integrated into the GET as a nested model.
...
class KeyDateCase(models.Model):
...
diagnoses_all_icd_10 = models.ManyToManyField(
'ICD10', through='CaseICD10Connection')
...
class CaseICD10Connection(models.Model):
case = models.ForeignKey('KeyDateCase', on_delete=models.CASCADE)
icd_10 = models.ForeignKey('ICD10', on_delete=models.CASCADE)
is_primary = models.BooleanField(default = False)
certainty = models.CharField(
max_length=1,
choices=CERTAINTY_CHOICES,
default='G',
)
class ICD10(models.Model):
primary_key_number = models.CharField(max_length=10, primary_key=True)
star_key_number = models.CharField(max_length=10, blank=True, null=True)
additional_key_number = models.CharField(
max_length=10, blank=True, null=True)
preferred_short_description = models.CharField(max_length=128, )
...
class KeyDateCaseViewSet(viewsets.ModelViewSet):
???
class KeyDateCaseSerializer(serializers.ModelSerializer):
???
How can I achieve this? What should my view and serializer look like?

Answer 1

Normally I workaround by indirect way by POST to through table and implement nested-create(). Please provide me more information if my answer is inaccurate.
models.py
from django.db import models
class ICD10(models.Model):
primary_key_number = models.CharField(max_length=10, primary_key=True)
star_key_number = models.CharField(max_length=10, blank=True, null=True)
additional_key_number = models.CharField(max_length=10, blank=True, null=True)
preferred_short_description = models.CharField(max_length=128, )
def __str__(self):
return f'{self.primary_key_number} {self.star_key_number}'
class CaseICD10Connection(models.Model):
case = models.ForeignKey('KeyDateCase', related_name='connections', related_query_name='key_date_cases', on_delete=models.CASCADE)
icd_10 = models.ForeignKey('ICD10', related_name='connections', related_query_name='icd_10s', on_delete=models.CASCADE)
is_primary = models.BooleanField(default=False)
certainty = models.CharField(max_length=1, default='G', )
class KeyDateCase(models.Model):
name = models.CharField(max_length=20)
diagnose_all_icd_10 = models.ManyToManyField(ICD10, related_name='icd10s', related_query_name='icd10s',
through=CaseICD10Connection)
serializers.py
from rest_framework import serializers
from keydatecases.models import KeyDateCase, ICD10, CaseICD10Connection
class KeyDateCaseSerializer(serializers.ModelSerializer):
class Meta:
model = KeyDateCase
fields = [
'id',
'name',
'diagnose_all_icd_10',
]
read_only_fields = ['id', 'diagnose_all_icd_10']
class ICD10Serializer(serializers.ModelSerializer):
class Meta:
model = ICD10
fields = [
'primary_key_number',
'star_key_number',
'additional_key_number',
'preferred_short_description',
]
class CaseICD10ConnectionSerializer(serializers.ModelSerializer):
case = KeyDateCaseSerializer()
icd_10 = ICD10Serializer()
class Meta:
model = CaseICD10Connection
fields = [
'case',
'icd_10',
'is_primary',
'certainty',
]
def create(self, validated_data) -> CaseICD10Connection:
# import ipdb;
# ipdb.set_trace()
# create key_date_case
key_date_case = KeyDateCase.objects.create(**validated_data.get('case'))
# create icd10
icd10 = ICD10.objects.create(**validated_data.get('icd_10'))
# create connection
conn = CaseICD10Connection.objects.create(
case=key_date_case, icd_10=icd10, is_primary=validated_data.get('is_primary'),
certainty=validated_data.get('certainty')
)
return conn
viewsets.py
from rest_framework import viewsets
from keydatecases.api.serializers import CaseICD10ConnectionSerializer
from keydatecases.models import CaseICD10Connection
class CaseICD10ConnectionViewSet(viewsets.ModelViewSet):
permission_classes = ()
queryset = CaseICD10Connection.objects.all()
serializer_class = CaseICD10ConnectionSerializer
My Repository:
I share my repository with many questions. Please do not mind it.
https://github.com/elcolie/tryDj2

Answer 2

In regards to creating or updating nested objects, the documentation actually has a great example. I would provide you a better one if I could. If there is anything confusing in the example, happy to explain it here.
If you follow this approach, your GET requests will expand the nested objects automatically for you.