DRF: Database not updating

Question

Following are my files. It is simply adding products based on subcategories and categories. Everything is working fine but the data is not being saved in the database. I am not sure where I am going wrong.

models.py

from django.db import models

class Category(models.Model):
    category = models.CharField(max_length=200)
    parent = models.ForeignKey('self', blank=True, null=True, related_name='children')

    class Meta:
        unique_together = ('parent' , 'category')

    def __str__(self):
        return self.category

class SubCategory(models.Model):
    subcategory = models.CharField(max_length=200)
    category = models.ForeignKey('Category', null=True, blank=True)
    parent = models.ForeignKey('self', blank=True, null=True, related_name='subchilren')

    class Meta:
        unique_together = ('parent' , 'subcategory')

    def __str__(self):
        return self.subcategory

class Product(models.Model):
    name = models.CharField(max_length=200)
    category = models.ForeignKey('Category', null=True, blank=True)
    subcategory = models.ForeignKey('SubCategory', null=True, blank=True)

    def __str__(self):
        return self.name

views.py

class AddProducts(APIView):
    serializer_class = AddProductsSerializer
    def post(self, request, format=None):
        data = request.data
        serializer = AddProductsSerializer(data=data)
        if serializer.is_valid(raise_exception=True):
            new_data = serializer.data
            return Response(new_data)
        return Response(serializer.errors, status=HTTP_400_BAD_REQUEST)

serializers.py

class AddProductsSerializer(serializers.ModelSerializer):
    class Meta:
        model = Product
        fields = ('id', 'name', 'category', 'subcategory')

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

        def update(self, instance, validated_data):
            instance.name =  validated_data.get('name', instance.name)
            instance.category = validated_data.get('category', instance.category)
            instance.subcategory = validated_data.get('subcategory', instance.subcategory)
            instance.save()
            return instance

if you open up the django shell, are you able to create a `Product` model via `p = Product.objects.create(name = 'some_name' ... )` and see it in the database? — Jason, Oct 31 '17 at 20:27
No. I tried `f = Product.objects.create(name='Shorts',category='Clothings',subcategor ...: y='Female')`, but it gave `ValueError: Cannot assign "'Clothings'": "Product.category" must be a "Category" instance.` I guess this is because field category is a foreign key, but I don't know how to do that for foreign key. — Yathartha Joshi, Oct 31 '17 at 20:34
yes, because you have ForeignKey as the field type for those fields. You need to get an instance of those models and use in the create call. Check out https://stackoverflow.com/questions/30017334/django-foreign-key-must-be-an-instance — Jason, Oct 31 '17 at 20:35
Something like: `cat = Category.objects.first(); sub_cat = SubCategory.obects.first(); p = Product.objects.create(name='Shorts', category=cat, subcategory=sub_cat)` — ettanany, Oct 31 '17 at 21:02

score 2 · Accepted Answer · answered Nov 01 '17 at 01:08

2

    if serializer.is_valid(raise_exception=True):
        serializer.save()
        new_data = serializer.data
        return Response(new_data)

add serializer.save() will call serializer create method when serializer has no instance.

answered Nov 01 '17 at 01:08

Ykh

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It worked! but I didn't understand why this happened. Before I used `instance.save()`, why was it not saved then, and what difference `serializer.save()` created? – Yathartha Joshi Nov 01 '17 at 04:12
1

`serializer.save()` will call `create` method in your `AddProductsSerializer` – Ykh Nov 01 '17 at 05:06

DRF: Database not updating

1 Answers1