CODEWITHSUNDEEP
djangodjango-rest-framework
user2492364
user2492364

Reputation: 6703

django rest framework : NOT NULL constraint failed

I want to make a post api,
users give me name and location and I save it
but I have a filed called datetime is not null,And it need to count
Please teach me how to deal with this situation

My models has 3 fileds: 

class Data(models.Model):
    name = models.CharField(max_length=50, null=True, blank=True)
    datetime = models.DateTimeField(auto_now=False, auto_now_add=False)
    location = models.CharField(max_length=255, null=True, blank=True)

serilizers.py 

class DataSerializer(serializers.ModelSerializer):
    class Meta:
        model = Data
        fields = (  'name','location' )

views.py 

class DataList(generics.ListCreateAPIView):
    queryset = Data.objects.all()
    serializer_class = DataSerializer

    def pre_save(self, obj):
        obj.datetime = datetime.now()

I find pre_save() function on the web ,
I thought it can help me save datetime datetime field
But ths answer is no

How can I save the datetime after I deal with it

Now I had error : 

NOT NULL constraint failed: data.datetime

Upvotes: 1

Views: 1742

Answers (3)

Mustapha-Belkacim
Mustapha-Belkacim

Reputation: 1821

I had a similar problem, I knew it was caused by the ORM trying to insert a null value in a non-nulable field, I was passing the right parameter to the API but the problem is with the serializer, add the datetime field to serilizers.py like this:

class DataSerializer(serializers.ModelSerializer):
class Meta:
    model = Data
    fields = (  'name', 'datetime', 'location' )

Upvotes: 0

Roba
Roba

Reputation: 688

It seams to me that you're actually trying to implement the functionality of auto_now_add=True, which you're specifically prevent it at the model level.

Why isn't auto_add_now good for what you're trying to achieve: the timestamp of object creation?

Upvotes: 0

Linovia
Linovia

Reputation: 20976

Since you're using 3.x your best option is to pass the serializer.save() an extra argument that will be pushed to the object's save:

class DataList(generics.ListCreateAPIView):
    queryset = Data.objects.all()
    serializer_class = DataSerializer

    def perform_create(self, serializer):
        serializer.save(datetime=datetime.now())

The serializer will add the datetime argument to validated_data used to create the instance.

Upvotes: 3

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