Django多店铺添加商品报错：Field 'id'期望数字却得到QuerySet

用户创建两个店铺后尝试添加商品时，返回Field 'id'错误；仅创建单个店铺时，操作正常无报错。

views.py 代码 #

def itemupload(request):
    user = request.user
    items = Items.objects.filter(user_id = request.user)
    
    
    try:
        # store = Store.objects.get(author= user)
        store = Store.objects.filter(author= user)
        
    except Store.DoesNotExist:
        store = None
        
   
    if request.method =='POST':
        itemsforms =ItemsForm(request.POST, request.FILES)
        imageforms = ImageForm(request.POST, request.FILES)
        
        
        file= request.FILES.getlist('image')
       
        if all([itemsforms.is_valid(), imageforms.is_valid()]):

            item = itemsforms.save(commit = False)
            item.user = request.user
            item.save()
            item.store.add(store)
            
            for i in file:
                Images.objects.create(item = item, image =i)
           
            return redirect('index')
        return redirect('itemupload')
        
    imageforms =ImageForm()
    itemsforms = ItemsForm()
    context = {
        'imageforms': imageforms,
        'itemsform':itemsforms,
        'items':items,
    }
    return render(request, 'jijiapp/itemform.html', context)

models.py 代码 #

class Store(models.Model):
    name = models.SlugField(unique =True, max_length=50)
    author = models.ForeignKey(User, on_delete=models.CASCADE, blank=False)
    create_date = models.DateTimeField(auto_now_add=True, null=True)
    discription=models.CharField(max_length=5000, null=True, blank=True)
    location =models.CharField(max_length=5000, null=True, blank=True)
    logo =models.ImageField(upload_to='logos/', default = '')
    
    def __str__(self):
        return '%s' % (self.name)
    
    class Meta:
        ordering = ['-name']
        verbose_name_plural = 'Store'

class Items(models.Model):
    user = models.ForeignKey(User, on_delete = models.CASCADE, null=True, blank=True)
    store = models.ManyToManyField(Store)
    title = models.CharField(max_length=10, null=True, blank =True)
    description = models.CharField(max_length=1000, null=True, blank=True)
    price = models.CharField(max_length=20, null=True, blank=True)
    phone = models.CharField(max_length=20, null=True, blank=True)
    location =models.CharField(max_length=20, null=True, blank=True)
    post_date = models.DateTimeField(auto_now_add=True, null=True, blank=True)
    thumbnails =models.ImageField(upload_to='thumbnails/', null=True, blank=True)

    def __str__(self):
        return self.title

    class Meta:
        ordering =['-post_date',]
        verbose_name_plural ='Items'

报错信息 #

System check identified no issues (0 silenced).
March 18, 2023 - 05:34:16
Django version 4.0, using settings 'jijiclone.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CTRL-BREAK.
tiis is the <generator object itemupload.<locals>.<genexpr> at 0x00000248939D25F0> and the is <QuerySet [<Store: X-Clusive Store>, <Store: GenFliX Exception Store>]>
Internal Server Error: /home/itemupload/
Traceback (most recent call last):
  File "C:\Users\Christopher\AppData\Local\Programs\Python\Python38\lib\site-packages\django\db\models\fields\__init__.py", line 1822, in get_prep_value
    return int(value)
TypeError: int() argument must be a string, a bytes-like object or a number, not 'QuerySet'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "C:\Users\Christopher\AppData\Local\Programs\Python\Python38\lib\site-packages\django\core\handlers\exception.py", line 47, in inner
    response = get_response(request)
  File "C:\Users\Christopher\AppData\Local\Programs\Python\Python38\lib\site-packages\django\core\handlers\base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "C:\Users\Christopher\jijiclone\jijiapp\views.py", line 74, in itemupload
    item.store.add(store)
  File "C:\Users\Christopher\AppData\Local\Programs\Python\Python38\lib\site-packages\django\db\models\fields\related_descriptors.py", line 949, in add
    self._add_items(
  File "C:\Users\Christopher\AppData\Local\Programs\Python\Python38\lib\site-packages\django\db\models\fields\related_descriptors.py", line 1125, in _add_items
    target_ids = self._get_target_ids(target_field_name, objs)
  File "C:\Users\Christopher\AppData\Local\Programs\Python\Python38\lib\site-packages\django\db\models\fields\related_descriptors.py", line 1072, in _get_target_ids
    target_ids.add(target_field.get_prep_value(obj))
  File "C:\Users\Christopher\AppData\Local\Programs\Python\Python38\lib\site-packages\django\db\models\fields\related.py", line 998, in get_prep_value
    return self.target_field.get_prep_value(value)
  File "C:\Users\Christopher\AppData\Local\Programs\Python\Python38\lib\site-packages\django\db\models\fields\__init__.py", line 1824, in get_prep_value
    raise e.__class__(
TypeError: Field 'id' expected a number but got <QuerySet [<Store: X-Clusive Store>, <Store: GenFliX Exception Store>]>.
[18/Mar/2023 05:35:26] "POST /home/itemupload/ HTTP/1.1" 500 94474

核心问题 #

store = Store.objects.filter(author= user)返回的是QuerySet对象（多个店铺的集合），而item.store.add()方法需要传入单个模型实例、实例ID，或者用*解包后的QuerySet。单个店铺时Django做了隐式兼容，多个店铺时直接传入QuerySet会触发类型错误，因为方法无法解析整个集合作为参数。

修复方法 #

将item.store.add(store)改为item.store.add(*store)，用*操作符解包QuerySet中的所有店铺实例，即可正确关联多个店铺到商品。

同时，原代码中try-except块对filter()无效（filter()无匹配时返回空QuerySet，不会抛出Store.DoesNotExist异常），可删除多余的异常处理，简化代码：

修改后的关键代码片段：

# 替换原try-except块，直接获取用户所有店铺
store = Store.objects.filter(author=user)

# ...

if all([itemsforms.is_valid(), imageforms.is_valid()]):
    item = itemsforms.save(commit=False)
    item.user = request.user
    item.save()
    # 用*解包QuerySet，批量添加关联店铺
    item.store.add(*store)
    
    for i in file:
        Images.objects.create(item=item, image=i)
    
    return redirect('index')

额外建议 #

如果业务需要让用户手动选择商品归属的店铺，可在ItemsForm中添加store字段，让用户提交表单时直接选择，无需自动关联所有店铺，更符合实际使用场景。

内容的提问来源于stack exchange，提问作者Wilfred Mathias