What should my django serializer def Update look like? - django

Question

I'm trying to add content for the first time using a DRF back-end written by someone else. I am receiving this error...
django_1 | AssertionError: The `.update()` method does not support writable nested fields by default.
django_1 | Write an explicit `.update()` method for serializer `myapp.tracker.serializers.MedicationSerializer`, or set `read_only=True` on nested serializer fields.
How can I write the Update method?
I've done rails before so I'm familiar with the concepts? So when I see a method "create" in my serilaizers.py I think "there must be a way to write a def Update here" But since I'm new to django I have NO IDEA what that method should actually look like ^_^. This is where I'm stuck.
Here is the serializers.py , models.py, and views.py code specific to the model I am trying to update...let me know if I need to post another files contents.
What should my def update method look like?
my serializer.py
class MedicationSerializer(serializers.HyperlinkedModelSerializer):
cat = CatSerializer()
class Meta:
model = Medication
fields = (
'id',
'cat',
'name',
'duration',
'frequency',
'dosage_unit',
'dosage',
'notes',
'created',
'modified',
'showRow',
)
def create(self, validated_data):
cat_data = validated_data.pop('cat')
cat_obj = Cat.objects.get(**cat_data)
medication = Medication.objects.create(cat=cat_obj, **validated_data)
return medication
the models.py looks like this
class Medication(models.Model):
cat = models.ForeignKey(Cat, blank=True, null=True)
name = models.CharField(max_length=100)
duration = models.TextField(blank=True, null=True)
frequency = models.CharField(max_length=2)
dosage_unit = models.CharField(max_length=2, default=Weight.MILLILITERS)
dosage = models.IntegerField(blank=True, null=True)
notes = models.CharField(max_length=2048, blank=True, null=True)
created = models.DateTimeField(blank=True, null=True)
modified = models.DateTimeField(blank=True, null=True)
showRow = models.BooleanField(default=True)
def save(self, *args, **kwargs):
# Save time Medication object modified and created times
self.modified = datetime.datetime.now()
if not self.created:
self.created = datetime.datetime.now()
super(Medication, self).save(*args, **kwargs)
def __str__(self):
if self.cat:
cat_name = self.cat.name
else:
cat_name = "NO CAT NAME"
return "{cat}: {timestamp}".format(cat=self.cat.name, timestamp=self.created)
and the views.py ....
class MedicationViewSet(viewsets.ModelViewSet):
queryset = Medication.objects.all()
serializer_class = MedicationSerializer
filter_fields = ('cat__slug', 'cat__name')
filter_backends = (django_filters.rest_framework.DjangoFilterBackend,)
Thank you for your time.

Answer 1

Try adding read-only=True to your Catserializer
class MedicationSerializer(serializers.HyperlinkedModelSerializer):
cat = CatSerializer(read_only=True)
class Meta:
model = Medication
fields = (
'id',
'cat',
'name',
'duration',
'frequency',
'dosage_unit',
'dosage',
'notes',
'created',
'modified',
'showRow',
)
def create(self, validated_data):
cat_data = validated_data.pop('cat')
cat_obj = Cat.objects.get(**cat_data)
medication = Medication.objects.create(cat=cat_obj, **validated_data)
return medication