Django 2.0 教程 - /polls/1/vote/ 'ReverseManyToOneDescriptor' 对象的 AttributeError 没有属性 'get'

Question

我以前在 SE 上遇到过这个错误，但它往往是针对以前版本的 Django - 我对 Django 的工作原理没有很好的理解。我已经完成了本教程的第 4 部分，并且一直到本教程为止。我真的不确定我做错了什么——此时大部分内容都是从教程中复制/粘贴的，以查看是否可以正常工作。我不完全是python saavy，所以如果有人能用相当简单的英语解释这个问题，我会很感激的。我知道这个问题与“投票”部分中的第 30 行有关 -

def vote(request, question_id):
    try:
        selected_choice = Question.choice_set.get(pk=request.POST['choice'])
    except (KeyError, Choice.DoesNotExist):
        # Redisplay the question voting form.
        return render(request, 'polls/detail.html', {
            'question': question,
            'error_message': "You didn't select a choice.",
        })
    else:
        selected_choice.votes += 1
        selected_choice.save()
        # Always return an HttpResponseRedirect after successfully dealing
        # with POST data. This prevents data from being posted twice if a
        # user hits the Back button.
        return HttpResponseRedirect(reverse('polls:results', args=(question.id,))) 

感谢 SE。

错误代码：

AttributeError at /polls/1/vote/
'ReverseManyToOneDescriptor' object has no attribute 'get'
Request Method: POST
Request URL:    http://localhost:8000/polls/1/vote/
Django Version: 2.0
Exception Type: AttributeError
Exception Value:    
'ReverseManyToOneDescriptor' object has no attribute 'get'
Exception Location: /Users/coreydickinson/mysite/DJDev/env1/mysite2/mysite3/polls/views.py in vote, line 30
Python Executable:  /Users/coreydickinson/mysite/DJDev/env1/bin/python
Python Version: 3.6.5
Python Path:    
['/Users/coreydickinson/mysite/DJDev/env1/mysite2/mysite3',
 '/Users/coreydickinson/mysite/DJDev/env1/lib/python36.zip',
 '/Users/coreydickinson/mysite/DJDev/env1/lib/python3.6',
 '/Users/coreydickinson/mysite/DJDev/env1/lib/python3.6/lib-dynload',
 '/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6',
 '/Users/coreydickinson/mysite/DJDev/env1/lib/python3.6/site-packages']
Server time:    Sat, 26 May 2018 03:16:49 +0000


Environment:


Request Method: POST
Request URL: http://localhost:8000/polls/1/vote/

Django Version: 2.0
Python Version: 3.6.5
Installed Applications:
['django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'polls.apps.PollsConfig']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware']



Traceback:

File "/Users/coreydickinson/mysite/DJDev/env1/lib/python3.6/site-packages/django/core/handlers/exception.py" in inner
  35.             response = get_response(request)

File "/Users/coreydickinson/mysite/DJDev/env1/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
  128.                 response = self.process_exception_by_middleware(e, request)

File "/Users/coreydickinson/mysite/DJDev/env1/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
  126.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/Users/coreydickinson/mysite/DJDev/env1/mysite2/mysite3/polls/views.py" in vote
  30.         selected_choice = Question.choice_set.get(pk=request.POST['choice'])

Exception Type: AttributeError at /polls/1/vote/
Exception Value: 'ReverseManyToOneDescriptor' object has no attribute 'get'

这是我用于各种文件的代码：

投票/网址：

from django.urls import path

from . import views

app_name = 'polls'
urlpatterns = [
    path('', views.IndexView.as_view(), name='index'),
    path('<int:pk>/', views.DetailView.as_view(), name='detail'),
    path('<int:pk>/results/', views.ResultsView.as_view(), name='results'),
    path('<int:question_id>/vote/', views.vote, name='vote'),
]

民意调查/观察：

from django.urls import reverse
from django.views import generic

from .models import Choice, Question


class IndexView(generic.ListView):
    template_name = 'polls/index.html'
    context_object_name = 'latest_question_list'

    def get_queryset(self):
        """Return the last five published questions."""
        return Question.objects.order_by('-pub_date')[:5]


class DetailView(generic.DetailView):
    model = Question
    template_name = 'polls/details.html'


class ResultsView(generic.DetailView):
    model = Question
    template_name = 'polls/results.html'


def vote(request, question_id):
    try:
        selected_choice = Question.choice_set.get(pk=request.POST['choice'])
    except (KeyError, Choice.DoesNotExist):
        # Redisplay the question voting form.
        return render(request, 'polls/detail.html', {
            'question': question,
            'error_message': "You didn't select a choice.",
        })
    else:
        selected_choice.votes += 1
        selected_choice.save()
        # Always return an HttpResponseRedirect after successfully dealing
        # with POST data. This prevents data from being posted twice if a
        # user hits the Back button.
        return HttpResponseRedirect(reverse('polls:results', args=(question.id,)))

投票/管理员：

from django.contrib import admin

from .models import Question

admin.site.register(Question)
polls/urls:

from django.urls import path

from . import views

app_name = 'polls'
urlpatterns = [
    path('', views.IndexView.as_view(), name='index'),
    path('<int:pk>/', views.DetailView.as_view(), name='detail'),
    path('<int:pk>/results/', views.ResultsView.as_view(), name='results'),
    path('<int:question_id>/vote/', views.vote, name='vote'),
]

民意调查/模板/民意调查/details.html：

<h1>{{ question.question_text }}</h1>
<ul>
{% for choice in question.choice_set.all %}
    <li>{{ choice.choice_text }}</li>
{% endfor %}
</ul>

<h1>{{ question.question_text }}</h1>

{% if error_message %}<p><strong>{{ error_message }}</strong></p>{% endif %}

<form action="{% url 'polls:vote' question.id %}" method="post">
{% csrf_token %}
{% for choice in question.choice_set.all %}
    <input type="radio" name="choice" id="choice{{ forloop.counter }}" value="{{ choice.id }}" />
    <label for="choice{{ forloop.counter }}">{{ choice.choice_text }}</label><br />
{% endfor %}
<input type="submit" value="Vote" />
</form>

投票/模板/投票/results.html：

<h1>{{ question.question_text }}</h1>

<ul>
{% for choice in question.choice_set.all %}
    <li>{{ choice.choice_text }} -- {{ choice.votes }} vote{{ choice.votes|pluralize }}</li>
{% endfor %}
</ul>

<a href="{% url 'polls:detail' question.id %}">Vote again?</a>
polls/templates/polls/index.html:

{% if latest_question_list %}
    <ul>
    {% for question in latest_question_list %}
        <li><a href="{% url 'polls:detail' question.id %}">{{ question.question_text }}</a></li>
    {% endfor %}
    </ul>
{% else %}
    <p>No polls are available.</p>
{% endif %}

mysite/settings.py

"""
Django settings for mysite3 project.

Generated by 'django-admin startproject' using Django 2.0.

For more information on this file, see
https://docs.djangoproject.com/en/2.0/topics/settings/

For the full list of settings and their values, see
https://docs.djangoproject.com/en/2.0/ref/settings/
"""

import os

# Build paths inside the project like this: os.path.join(BASE_DIR, ...)
BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))


# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/2.0/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = '*8a@se$l_8v%(-xyz=!!=jgvyjyn611zqw(dqroejvkk^o9%co'

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = True

ALLOWED_HOSTS = []


# Application definition

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'polls.apps.PollsConfig',
]

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]

ROOT_URLCONF = 'mysite3.urls'

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

WSGI_APPLICATION = 'mysite3.wsgi.application'


# Database
# https://docs.djangoproject.com/en/2.0/ref/settings/#databases

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
    }
}


# Password validation
# https://docs.djangoproject.com/en/2.0/ref/settings/#auth-password-validators

AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
    },
]


# Internationalization
# https://docs.djangoproject.com/en/2.0/topics/i18n/

LANGUAGE_CODE = 'en-us'

TIME_ZONE = 'UTC'

USE_I18N = True

USE_L10N = True

USE_TZ = True


# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/2.0/howto/static-files/

STATIC_URL = '/static/'

Answer 1

这是引发错误的行：

selected_choice = Question.choice_set.get(pk=request.POST['choice'])

基本上，您需要在问题模型的实例上调用choice_set，而不是在模型本身上。

所以这样的事情可能会起作用：

question = Question.objects.get(pk=question_id)
selected_choice = question.choice_set.get(pk=request.POST['choice'])