DRF TypeError 'type' object is not iterable

Question

我正在创建我的第一个DRF API，并且在尝试使用GET请求访问我的数据时，我遇到了一个奇怪的TypeError，出现了以下错误：

'type' object is not iterable

以下是一些代码片段。

models.py

from django.db import models

# Create your models here.

class Expediteur(models.Model):
    nom = models.CharField(max_length=50)
    prenom = models.CharField(max_length=100)
    adresse = models.CharField(max_length=200)
    tel = models.IntegerField()

views.py

from django.shortcuts import render, get_object_or_404
from rest_framework import viewsets
from rest_framework.views import APIView
from rest_framework.response import Response
from polls.serializers import ExpediteurSerializer, DestinataireSerializer, LettrePrioSerializer, TypeLettreRecoSerializer, LettreRecoSerializer, TimbrePrioSerializer, TimbreRecoSerializer
from polls.models import Expediteur, Destinataire, LettrePrio, TypeLettreReco, LettreReco, TimbrePrio, TimbreReco
from rest_framework import status, HTTP_HEADER_ENCODING

import json
import datetime

from django.http import HttpResponseRedirect, HttpResponse, Http404
from django.core.urlresolvers import reverse
from django.contrib.auth.decorators import user_passes_test
from django.contrib.auth import login
from django.core.exceptions import ObjectDoesNotExist
from django.views.decorators.csrf import csrf_exempt
from django.utils.timezone import get_current_timezone
from django.db.models.query import QuerySet

# Create your views here.

class ExpeViewSet(APIView):
    QuerySet = Expediteur.objects.all()
    serializer_class = ExpediteurSerializer

    def get(self, request):
        serializer = ExpediteurSerializer(QuerySet, many=True)
        return Response(serializer.data)

    def post(self, request):
        serializer = self.serializer_class(data=request.DATA)
        return Response(status=status.HTTP_201_CREATED)

serializers.py

from rest_framework import serializers
from polls.models import Expediteur, Destinataire, LettrePrio, TypeLettreReco, LettreReco, TimbrePrio, TimbreReco


class ExpediteurSerializer(serializers.ModelSerializer):
    class Meta:
        model = Expediteur

我也留下了Traceback以获取更多信息：

Environment:


Request Method: GET
Request URL: http://0.0.0.0:8000/polls/expediteur/

Django Version: 1.7.1
Python Version: 2.7.6
Installed Applications:
('django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'rest_framework',
 'polls')
Installed Middleware:
('django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware')


Traceback:
File "/Library/Python/2.7/site-packages/Django-1.7.1-py2.7.egg/django/core/handlers/base.py" in get_response
  111.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/Library/Python/2.7/site-packages/Django-1.7.1-py2.7.egg/django/views/decorators/csrf.py" in wrapped_view
  57.         return view_func(*args, **kwargs)
File "/Library/Python/2.7/site-packages/Django-1.7.1-py2.7.egg/django/views/generic/base.py" in view
  69.             return self.dispatch(request, *args, **kwargs)
File "/Library/Python/2.7/site-packages/rest_framework/views.py" in dispatch
  452.             response = self.handle_exception(exc)
File "/Library/Python/2.7/site-packages/rest_framework/views.py" in dispatch
  449.             response = handler(request, *args, **kwargs)
File "/Users/mehdi/rendu/ProjectWeek/CUP/polls/views.py" in get
  29.         return Response(serializer.data)
File "/Library/Python/2.7/site-packages/rest_framework/serializers.py" in data
  618.         ret = super(ListSerializer, self).data
File "/Library/Python/2.7/site-packages/rest_framework/serializers.py" in data
  213.                 self._data = self.to_representation(self.instance)
File "/Library/Python/2.7/site-packages/rest_framework/serializers.py" in to_representation
  568.             self.child.to_representation(item) for item in iterable

Exception Type: TypeError at /polls/expediteur/
Exception Value: 'type' object is not iterable

- Mehdi

Answer 1

如果您想列出所有的expediteur实例，应该使用list视图而不是get。请记住，get是用于检索一个实例的。

此外，在您的导入中，您有from django.db.models.query import QuerySet，然后当您尝试ExpediteurSerializer(QuerySet, many=True)时，您正在尝试序列化先前导入的QuerySet类型。要获取您定义的QuerySet，需要使用self.但我建议只使用queryset。

class ExpeViewSet(GenericAPIView):
      queryset = Expediteur.objects.all() 
      serializer_class = ExpediteurSerializer


      def list(self,request):
          queryset  = self.Expediteur.objects.all() 
          serializer = ExpediteurSerializer(self.get_queryset(), many=True)
          return Response(serializer.data)

- levi

---

谢谢你的回答。我尝试了你给我的代码，但是我遇到了另一个错误：AttributeError 'ExpeViewSet'对象没有'get_queryset'属性。 - Mehdi

QuerySet未定义，您的意思是self.QuerySet，但是QuerySet只会在服务器启动时被评估一次，永远不会更新。 - djangonaut

@user640916，QuerySet已被定义，请检查OP代码。但我也将其添加为小写。 - levi

@levi，请检查变量的作用域。QuerySet 不是函数“list”的本地变量。 - djangonaut

@Mehdi啊，那是因为你需要更新你的urls.py文件，添加list方法和一个GET请求。 - levi

Answer 2

我看到你使用了QuerySet，但它应该是小写字母。

试试这个：

from rest_framework.generics import GenericAPIView

class ExpeViewSet(GenericAPIView):
    queryset = Expediteur.objects.all()  # lowercase!
    serializer_class = ExpediteurSerializer

    def get(self, request):
        serializer = self.serializer_class(self.get_queryset(), many=True)
        return Response(serializer.data)

- djangonaut

---

实际上这不是问题。OP已经导入了from django.db.models.query import QuerySet，然后他试图序列化导入的QuerySet类型。这不是由小写字母引起的。 - levi

你给一个可行的解决方案点了踩？你正在给QuerySet分配一些Django导入的东西，这显然是错误的。在我的踩之后，你进行了多次编辑。请理性对待！ - djangonaut

编辑您的答案以点赞，但您也对正确答案进行了踩。 - levi

Answer 3

在我的情况下，我没有从models.Model继承Model。

例如：class Document: ... 应该是： class Document(models.Model): ...

- prat_bhan