Django REST框架无法正确序列化POST数据。

huangapple
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英文:

Django rest framework post data not being serialized properly

问题

I have 2 models

  1. class MenuItem(models.Model):
  2.     title = models.CharField(max_length=255, db_index=True)
  3.     price = models.DecimalField(max_digits=6, decimal_places=2, db_index=True)
  4.     featured = models.BooleanField(db_index=True)
  5.     category = models.ForeignKey(Category, on_delete=models.PROTECT)
  6.     def __str__(self):
  7.         return f'{self.title}';
  9. class Cart(models.Model):
  10.     user = models.ForeignKey(User, on_delete=models.CASCADE)
  11.     menuitem = models.ForeignKey(MenuItem, on_delete=models.CASCADE)
  12.     quantity = models.SmallIntegerField()
  13.     unit_price = models.DecimalField(max_digits=6, decimal_places=2, default=0)
  14.     price = models.DecimalField(max_digits=6, decimal_places=2, default=0)
  16.     class Meta:
  17.         unique_together = ('menuitem', 'user')

The MenuItem.price should be equal to Cart.unit_price for a particular object. Now the problem I'm having is writing the serializer for the Cart Model.

So far I've tried this:

  1. class MenuItemSerializer(serializers.HyperlinkedModelSerializer):
  2.     title = serializers.CharField(max_length=255)
  3.     price = serializers.DecimalField(max_digits=6, decimal_places=2)
  4.     category_id = serializers.IntegerField(write_only=True)
  5.     category = CategorySerializer(read_only=True)
  6.     featured = serializers.BooleanField()    
  7.     class Meta:
  8.         model = MenuItem
  9.         fields = ['title', 'price', 'category', 'category_id', 'featured']
  10.         depth = 1
  12. class CartSerializer(serializers.ModelSerializer):
  13.     user = serializers.HiddenField(
  14.         default=serializers.CurrentUserDefault(),
  15.     )
  16.     menu_item = MenuItemSerializer
  17.     quantity = serializers.IntegerField()
  18.     # unit_price = serializers.DecimalField(max_digits=6, decimal_places=2, style={'input_type':'hidden'})
  19.     unit_price = serializers.ReadOnlyField(source="menuitem.price", read_only=True)
  20.     price = SerializerMethodField()
  21.     class Meta:
  22.         model = Cart
  23.         fields = ['user', 'menuitem', 'unit_price', 'quantity', 'price']
  25.     def get_price(self, obj):
  26.         return obj.quantity * obj.unit_price

and then the relevant view

  1. class Cart(mixins.ListModelMixin,
  2.            mixins.DestroyModelMixin,
  3.            generics.GenericAPIView):
  4.     queryset = Cart.objects.all()
  5.     serializer_class = CartSerializer
  7.     def get(self, request, *args, **kwargs):
  8.         return self.list(request, *args, **kwargs)
  9.     
  10.     def create(self, request, *args, **kwargs):
  11.         serializer = self.get_serializer(data=request.data)
  12.         serializer.is_valid(raise_exception=True)
  13.         serializer.save()
  14.         return Response(serializer.data, status=status.HTTP_201_CREATED)
  15.     
  16.     def post(self, request, *args, **kwargs):
  17.         return self.create(request, *args, **kwargs)

However, this does not return the required value for price. It only returns 0.

I'm a Django newbie, and this has been driving me nuts. It would be nice if someone could help out.

This is an example response that I'm getting:

  1. {
  2.     "menuitem": 1,
  3.     "unit_price": 2.5,
  4.     "quantity": 3,
  5.     "price": 0
  6. }
英文:

I have 2 models

  1. class MenuItem(models.Model):
  2.     title = models.CharField(max_length=255, db_index=True)
  3.     price = models.DecimalField(max_digits=6, decimal_places=2, db_index=True)
  4.     featured = models.BooleanField(db_index=True)
  5.     category = models.ForeignKey(Category, on_delete=models.PROTECT)
  6.     def __str__(self):
  7.         return f'{self.title}'
  9. class Cart(models.Model):
  10.     user = models.ForeignKey(User, on_delete=models.CASCADE)
  11.     menuitem = models.ForeignKey(MenuItem, on_delete=models.CASCADE)
  12.     quantity = models.SmallIntegerField()
  13.     unit_price = models.DecimalField(max_digits=6, decimal_places=2, default=0)
  14.     price = models.DecimalField(max_digits=6, decimal_places=2, default=0)
  16.     class Meta:
  17.         unique_together = ('menuitem', 'user')

The MenuItem.price should be equal to Cart.unit_price for a particular object. Now the problem I'm having is writing the serializer for the Cart Model.

So far I've tried this:

  1. class MenuItemSerializer(serializers.HyperlinkedModelSerializer):
  2.     title = serializers.CharField(max_length=255)
  3.     price = serializers.DecimalField(max_digits=6, decimal_places=2)
  4.     category_id = serializers.IntegerField(write_only=True)
  5.     category = CategorySerializer(read_only=True)
  6.     featured = serializers.BooleanField()    
  7.     class Meta:
  8.         model = MenuItem
  9.         fields = ['title', 'price', 'category', 'category_id', 'featured']
  10.         depth = 1
  12. class CartSerializer(serializers.ModelSerializer):
  13.     user = serializers.HiddenField(
  14.         default=serializers.CurrentUserDefault(),
  15.     )
  16.     menu_item = MenuItemSerializer
  17.     quantity = serializers.IntegerField()
  18.     # unit_price = serializers.DecimalField(max_digits=6, decimal_places=2, style={'input_type':'hidden'})
  19.     unit_price = serializers.ReadOnlyField(source="menuitem.price", read_only=True)
  20.     price = SerializerMethodField()
  21.     class Meta:
  22.         model = Cart
  23.         fields = ['user', 'menuitem', 'unit_price', 'quantity', 'price']
  25.     def get_price(self, obj):
  26.         return obj.quantity * obj.unit_price

and then the relevant view

  1. class Cart(mixins.ListModelMixin,
  2.            mixins.DestroyModelMixin,
  3.            generics.GenericAPIView):
  4.     queryset = Cart.objects.all()
  5.     serializer_class = CartSerializer
  7.     def get(self, request, *args, **kwargs):
  8.         return self.list(request, *args, **kwargs)
  9.     
  10.     def create(self, request, *args, **kwargs):
  11.         serializer = self.get_serializer(data=request.data)
  12.         serializer.is_valid(raise_exception=True)
  13.         serializer.save()
  14.         return Response(serializer.data, status=status.HTTP_201_CREATED)
  15.     
  16.     def post(self, request, *args, **kwargs):
  17.         return self.create(request, *args, **kwargs)

However this does not return the required value for price. It only returns 0.

I'm a django newbie and this has been driving me nuts. It would be nice if someone could help out.

This is an example response that I'm getting:
{
"menuitem": 1,
"unit_price": 2.5,
"quantity": 3,
"price": 0
}

答案1

得分: 0

你在Cart模型中存储了price和unit_price，以及MenuItem模型。

在CartSerializer中，在get_price方法内，你使用Cart的unit_price来计算最终价格，而不是使用MenuItem的unit_price，而CartSerializer的unit_price字段具有source="menuitem.price"。

因此，在你分享的响应中，你从菜单项模型中得到了"unit_price": 2.5，而你的价格是通过使用Cart模型的unit_price字段计算的，这个字段必须是0，因为它的默认值是0。因此，你的最终价格计算结果为3（数量）* 0（来自Cart模型的价格）= 0，而它应该是3（数量）* 2.5（来自MenuItem模型的价格）= 7.5。

确保从Cart模型中删除多余的字段，以减少混淆，并更新CartSerializer中的get_price方法如下：

  1. def get_price(self, obj):
  2.     return obj.quantity * obj.menuitem.price
英文:

You are storing price and unit_price in the Cart model along with the MenuItem model.

In the CartSerializer, inside the get_price method, you are computing the final price by using the unit_price of the Cart, not the MenuItem, while the unit_price field of the CartSerializer has source="menuitem.price".

So in the response you shared, you are getting "unit_price": 2.5 from the menu item model, while your price is being calculated by using the unit_price field of Cart model, which must be 0, as it defaults to 0. Hence, your final price results in 3 (quantity) * 0 (price from Cart model) = 0, while it should be 3 (quantity) * 2.5 (price from MenuItem model) = 7.5.

Make sure that you remove redundant fields from the Cart model so it is less confusing, and update the get_price method in the CartSerializer to:

  1. def get_price(self, obj):
  2.     return obj.quantity * obj.menuitem.price

huangapple
  • 本文由 发表于 2023年6月1日 00:55:22
  • 转载请务必保留本文链接：https://go.coder-hub.com/76375782.html
  • django
  • django-rest-framework
  • django-serializer
  • python
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