AssertionError：期望从视图返回一个`Response`、`HttpResponse`或`HttpStreamingResponse`，但收到`<class 'NoneType'>`答案

【问题标题】：AssertionError: Expected a `Response`, `HttpResponse` or `HttpStreamingResponse` to be returned from view, but received `<class 'NoneType'>`AssertionError：期望从视图返回一个`Response`、`HttpResponse`或`HttpStreamingResponse`，但收到`<class 'NoneType'>`
【发布时间】：2020-02-13 16:44:16
【问题描述】：

我有以下型号 -

class Userdetails(models.Model):

id = models.AutoField(primary_key=True)
name = models.CharField(max_length=200, blank=True, null=True)
userno = models.CharField(max_length=200, blank=True, null=True

和下面的视图 -

 @api_view(['GET', 'POST'])
    def useroptions(request):        # to create new user
        if request.method == 'GET':
            names = Userdetails.objects.values("name","userno","id")
            return Response(names)

        elif request.method == 'POST':
            count = Userdetails.objects.count()
            serializer = userdetailsSerializer(data=request.data)
            usernos = Userdetails.objects.values("userno")
            names = Userdetails.objects.values("name")
            list_of_names = []
            for ele in names:
                list_of_names.append(ele["name"])

            list_of_usernos = []
            for ele in usernos:
                list_of_usernos.append(ele["userno"])

这在 CMD 上给了我这个错误 -

Internal Server Error: /view/pardel/2/multiuser
Traceback (most recent call last):
  File "/home/hostbooks/django1/myproject/lib/python3.6/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/home/hostbooks/django1/myproject/lib/python3.6/site-packages/django/core/handlers/base.py", line 115, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/home/hostbooks/django1/myproject/lib/python3.6/site-packages/django/core/handlers/base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/hostbooks/django1/myproject/lib/python3.6/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/home/hostbooks/django1/myproject/lib/python3.6/site-packages/django/views/generic/base.py", line 71, in view
    return self.dispatch(request, *args, **kwargs)
  File "/home/hostbooks/django1/myproject/lib/python3.6/site-packages/rest_framework/views.py", line 507, in dispatch
    self.response = self.finalize_response(request, response, *args, **kwargs)
  File "/home/hostbooks/django1/myproject/lib/python3.6/site-packages/rest_framework/views.py", line 422, in finalize_response
    % type(response)
AssertionError: Expected a `Response`, `HttpResponse` or `HttpStreamingResponse` to be returned from the view, but received a `<class 'NoneType'>`
[13/Feb/2020 08:09:14] "POST /view/pardel/2/multiuser HTTP/1.1" 500 17234

我没有得到这个错误的原因，请我解决这个错误。

【问题讨论】：

标签： python django python-3.x django-rest-framework django-views

【解决方案1】：

您没有为POST 请求返回http 响应对象。来自django docs：

您编写的每个视图都负责实例化、填充和返回一个 HttpResponse。

更改您的视图以返回发布请求的 http 响应。

@api_view(['GET', 'POST'])
def useroptions(request):        # to create new user
    if request.method == 'GET':
        names = Userdetails.objects.values("name","userno","id")
        return Response(names)

    elif request.method == 'POST':
        count = Userdetails.objects.count()
        serializer = userdetailsSerializer(data=request.data)
        usernos = Userdetails.objects.values("userno")
        names = Userdetails.objects.values("name")
        list_of_names = []
        for ele in names:
            list_of_names.append(ele["name"])

        list_of_usernos = []
        for ele in usernos:
            list_of_usernos.append(ele["userno"])
        context = {'data': serializer.data, 'names': list_of_names, 'usernos': list_of_usernos} # change it as per your requirement
        return Response(context)

【讨论】：

【解决方案2】：

您收到此错误是因为您没有从视图中返回。

代码应该是这样的。

@api_view(['GET', 'POST'])
    def useroptions(request):        # to create new user
        if request.method == 'GET':
            names = Userdetails.objects.values("name","userno","id")
            return Response(names)

        elif request.method == 'POST':
            count = Userdetails.objects.count()
            serializer = userdetailsSerializer(data=request.data)
            usernos = Userdetails.objects.values("userno")
            names = Userdetails.objects.values("name")
            list_of_names = []
            for ele in names:
                list_of_names.append(ele["name"])

            list_of_usernos = []
            for ele in usernos:
                list_of_usernos.append(ele["userno"])

            response_dict = {}
            # update response_dict with whatever you want to send in response
            return Response(response_dict)

【讨论】：