Python Django-Rest-Framework update user on data creation

Question

Assuming I have 2 models, one User, the other Post. A user can create posts. A user has a field called 'exp_pts' as an IntegerField. This is meant to increment by say 30 when the user creates a post.

I assume I would have to use the create() method in the PostSerializer. This is my current serializer for Posts (currently not working due to the create() method not working as intended)

class PostSerializer(serializers.ModelSerializer):

    class Meta:
        model = Post
        fields = ('id', 'user', 'kingdom', 'post_type', 'file_path',
                  'title', 'description', 'created_at', 'updated_at')

    def to_representation(self, instance):
        data = super().to_representation(instance)
        data['user'] = SimpleUserSerializer(
            User.objects.get(pk=data['user'])).data
        data['kingdom'] = KingdomSerializer(
            Kingdom.objects.get(pk=data['kingdom'])).data
        return data

    # This is not yet working
    def create(self, validated_data):
        user = validated_data.pop('user')
        user.exp_pts += 30
        user.save()
        return user

What is a way to do the above? If the create() method isn't adequate then what other way is there to achieve this? Any help much appreciated. Thank you.

Hafnernuss · Accepted Answer · 2020-09-03 08:55:04Z

2

Your create method is wrong. It should be more like that:

def create(self, validated_data):
        user = validated_data.pop('user')
        user.exp_pts += 30
        user.save()

        return super().create(validated_data)

Your serializer's create method has to return an instance of the created Post, not User. Since the actual creation can be handled by DRF itself, just return super().create(validated_data).

edited Sep 3, 2020 at 8:55

answered Sep 3, 2020 at 8:48

Hafnernuss

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3 Comments

Sorin Burghiu Over a year ago

Thank you for the comment, I see what you mean, however this is still giving this error:django.db.utils.IntegrityError: NOT NULL constraint failed: api_post.user_id

Hafnernuss Over a year ago

ah, your post model has a user FK. then dont pop the the user from the dict, but get it.

Sorin Burghiu Over a year ago

replacing 'pop' with 'get' did it. Thank you

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