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django - AttributeError：“产品”对象没有属性“过滤器”

问题描述

我正在尝试访问链接“ http://127.0.0.1:8000/products/2 ”，其中我正在使用通用视图（DetailsView），并且在该视图中我想使用我的自定义模型管理器。但是我收到错误消息，指出 AttributeError：“产品”对象没有属性“过滤器”。

我正在使用 python version3.8 和 django version 2.2.6

# ModelManager
#-----------------------------------------------
class ProductManager(models.Manager):
    def get_by_id(self,id):
        qs = self.get_queryset().filter(id=id)
        if qs.count() == 1:
            return qs.first()
        return None



# View
#-----------------------------------------------
class ProductDetailView(DetailView):
    # queryset = Product.objects.all( )
    def get_queryset(self, *args, **kwargs):
        request = self.request
        pk = self.kwargs.get("pk")
        instance = Product.objects.get_by_id(pk)
        if instance is None:
            raise Http404("Product Couldn't be found")
        return instance

＃ 错误

Internal Server Error: /products/2
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/django/core/handlers/base.py", line 115, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/django/core/handlers/base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/django/views/generic/base.py", line 71, in view
    return self.dispatch(request, *args, **kwargs)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/django/views/generic/base.py", line 97, in dispatch
    return handler(request, *args, **kwargs)
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/django/views/generic/detail.py", line 106, in get
    self.object = self.get_object()
  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/django/views/generic/detail.py", line 36, in get_object
    queryset = queryset.filter(pk=pk)
AttributeError: 'Product' object has no attribute 'filter'
[22/Oct/2019 18:51:56] "GET /products/2 HTTP/1.1" 500 75133

标签： djangodjango-models

解决方案

[ get_queryset(..)Django-doc]需要一个queryset，而不是一个实例。您应该改写get_object(..)[Django-doc]：

class ProductDetailView(DetailView):

    def get_object(self, *args, **kwargs):
        request = self.request
        pk = self.kwargs.get('pk')
        instance = Product.objects.get_by_id(pk)
        if instance is None:
            raise Http404('Product Couldn't be found')
        return instance

覆盖get_queryset失败的原因是因为如果您返回单个Product对象，则默认值get_object将调用get_queryset，然后调用.filter(..)该结果。但是单身Product当然没有.filter(..)办法。

请注意，将您的经理实施为：

class ProductManager(models.Manager):
    def get_by_id(self,id):
        try:
            return self.get_queryset().get(id=id)
        except (self.model.DoesNotExist, self.model.MultipleObjectsReturned):
            return None

因为这里我们只会对数据库进行一次查询，而不是多次查询。

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