通过选择不同的大小来更改价格电子商务应用程序时，我在不支持的操作数类型中收到错误

unsupported operand type(s) for +: 'int' and 'str'
Internal Server Error: /product/t-shirts/
Traceback (most recent call last):
  File "C:\Python311\Lib\site-packages\django\core\handlers\exception.py", line 55, in inner
    response = get_response(request)
               ^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python311\Lib\site-packages\django\core\handlers\base.py", line 204, in _get_response
    self.check_response(response, callback)
  File "C:\Python311\Lib\site-packages\django\core\handlers\base.py", line 332, in check_response
    raise ValueError(
ValueError: The view products.views.get_product didn't return an HttpResponse object. It returned None instead.
[20/Jul/2024 12:48:11] "GET /product/t-shirts/?size=XL HTTP/1.1" 500 68697

这是我的 products.models 页面

from django.db import models

from base.models import BaseModel

from django.utils.text import slugify


class Category(BaseModel):
    category_name = models.CharField(max_length=100)

    slug = models.SlugField(unique=True, null=True, blank=True)

    category_image = models.ImageField(upload_to="categories")

    def save(self, *args, **kwargs):
        self.slug = slugify(self.category_name)

        super(Category, self).save(*args, **kwargs)

    def __str__(self) -> str:
        return self.category_name


class ColorVariant(BaseModel):
    color_name = models.CharField(max_length=100)

    price = models.CharField(max_length=100)

    def __str__(self) -> str:
        return self.color_name


class SizeVariant(BaseModel):
    size_name = models.CharField(max_length=100)

    price = models.CharField(max_length=100)

    def __str__(self) -> str:
        return self.size_name


class Product(BaseModel):
    product_name = models.CharField(max_length=100)

    slug = models.SlugField(unique=True, null=True, blank=True)

    categorys = models.ForeignKey(
        Category,
        on_delete=models.CASCADE,
        related_name="products",
        blank=False,
        null=True,
    )
    price = models.IntegerField()

    products_description = models.TextField()

    color_variant = models.ManyToManyField(ColorVariant, blank=True)

    size_variant = models.ManyToManyField(SizeVariant, blank=True)

    def save(self, *args, **kwargs):
        self.slug = slugify(self.product_name)
        super(Product, self).save(*args, **kwargs)

    def __str__(self) -> str:
        return self.product_nam

    def get_product_price_by_size(self, size):
        return self.price + str(SizeVariant.objects.get(size_name=size).price)


class ProductImage(BaseModel):
    products = models.ForeignKey(
        Product, on_delete=models.CASCADE, related_name="product_images"
    )

    image = models.ImageField(upload_to="product")

The error message "unsupported operand type(s) for +: 'int' and 'str'" means that you are trying to add an integer and a string together, which is not allowed in Python.

Looking at your code, the problem lies in the get_product_price_by_size method of your Product model:

def get_product_price_by_size(self, size):
    return self.price + str(SizeVariant.objects.get(size_name=size).price) 

Here's what's happening:

1. self.price is an integer. You defined it as price = models.IntegerField() in the Product model.
2. SizeVariant.objects.get(size_name=size).price retrieves a string. You defined price as a CharField in the SizeVariant model.
3. You're trying to add the integer ( self.price ) and the string ( SizeVariant.objects.get(size_name=size).price ) together. This results in the "unsupported operand type(s)" error because Python doesn't know if you want to concatenate the values as strings or add them as numbers.

To fix this, you should ensure both values are treated as numbers:

1. Change price in SizeVariant to an IntegerField : ```python class SizeVariant(BaseModel): size_name = models.CharField(max_length=100) price = models.IntegerField() # Change to IntegerField

   def str (self) -> str: return self.size_name ```

2. Modify the get_product_price_by_size method: python def get_product_price_by_size(self, size): size_variant = SizeVariant.objects.get(size_name=size) return self.price + size_variant.price

This modification ensures that both self.price and size_variant.price are integers before they are added together.

After making these changes, remember to run migrations:

python manage.py makemigrations
python manage.py migrate

This will update your database schema to reflect the changes you made to your model.