`TypeError` when calling create(). You may need to make the field read-only, or override the create() method

Question

Not sure what's going on here. I'm trying to perform create a new instance via Django-rest-framework. What am I doing wrong?

There are a few read-only fields being submitted back. I've tried marking them as read-only via read_only_fields in the serializer, as well as specifying them as editable=False within the model's fields.

Note: I would prefer to avoid specifying my own create method if possible. This should work via standard functionality as documented here

when POSTing the following:

{
  "displayName": "New test",
  "backgroundColour": "#4d3567",
  "foregroundColour": "#FFFFFF",
  "helpText": "test",
  "description": "test",
  "comment": "test."
}

i'm getting:

TypeError at /api/v1/classifications/
Got a `TypeError` when calling `ClassificationLabel.objects.create()`. This may be because you have a writable field on the serializer class that is not a valid argument to `ClassificationLabel.objects.create()`. You may need to make the field read-only, or override the ClassificationLabelListSerializer.create() method to handle this correctly.

models.py:

class ClassificationLabel(models.Model):
    """
    this model is used to create all instances of classifications 
    labels that will be displayed to a user
    """
    displayName = models.CharField('Classification label display name', max_length = 32)
    helpText = models.TextField('Explanatory text about this label', max_length = 140, blank=True)
    backgroundColour = models.CharField('Hex code for background colour including Alpha', max_length=8)
    foregroundColour = models.CharField('Hex code for foreground colour include Alpha', max_length=8)
    description = models.TextField('Description of this label', max_length = 256, blank=True)
    comment = models.TextField('Internal comments for this label', max_length = 1024, blank=True)
    lastChanged = models.DateTimeField('last changed timestamp', auto_now=True, editable=False)
    identifier = models.CharField('Classification label ID', max_length = 128, blank=True, editable=False)
    revision = models.PositiveIntegerField('Revision number for this label', default=1, editable=False)
    #placeholder for lastChangedBy

    def clean(self):
        #the following code generates a unique identifier and checks it for collisions against existing identifiers
        if not self.identifier:
            stringCheck = False
            while stringCheck is False:
                newString = str(uuid.uuid4())
                newString.replace('-', '')
                doesStringExist = ClassificationLabel.objects.filter(identifier=newString).count()
                if doesStringExist == 0:
                    stringCheck = True
            self.identifier = newString

    def __str__(self):
        return self.displayName + " - " + self.identifier

    def save(self, force_insert=False, force_update=False):
        self.revision += 1
        super(ClassificationLabel, self).save(force_insert, force_update) # Call the "real" save() method.

serializer:

class ClassificationLabelListSerializer(serializers.ModelSerializer):
    class Meta:
        model = ClassificationLabel
        fields = ('displayName', 'helpText', 'identifier', 'backgroundColour', 'foregroundColour', 'comment', 'description', 'lastChanged', 'revision')
        #read_only_fields = ('identifier', 'lastChanged', 'revision',)

views.py

class ClassificationLabelList(mixins.ListModelMixin,generics.GenericAPIView, mixins.CreateModelMixin):
queryset = ClassificationLabel.objects.all()
serializer_class = ClassificationLabelListSerializer

def get(self, request, *args, **kwargs):
    return self.list(request, *args, **kwargs)

def post(self, request, *args, **kwargs):
    return self.create(request, *args, **kwargs)

what seems to have fixed it an updated save() method seems to have fixed this. updated code below:

    def save(self, *args, **kwargs):
        self.revision += 1
        super(ClassificationLabel, self).save() # Call the "real" save() method.

Answer 1

Maybe try something like this in your serializer,

class ClassificationLabelListSerializer(serializers.ModelSerializer):
    lastChanged = serializers.DateTimeField(read_only=True)
    identifier = serializers.CharField(read_only=True)
    revision = serializers.IntegerField(read_only=True)
    class Meta:
        model = ClassificationLabel
        fields = ('displayName', 'helpText', 'identifier', 'backgroundColour', 'foregroundColour', 'comment', 'description', 'lastChanged', 'revision')

    def create(self, validated_data):
        return ClassificationLabel.objects.create(**validated_data)

Also, edit the save method in your models.py,

def save(self, *args, **kwargs):
    self.revision += 1
    return super(ClassificationLabel, self).save(*args, **kwargs) #