未定义 'snippets' [Django Rest]

Question

我正在学习Django REST框架的教程，当我尝试用命令行工具curl访问 http://127.0.0.1:8000/snippets 时，出现了错误。我对Python、这个框架和Django都很陌生，所以不知道该从哪里入手。

代码看起来没什么问题，因为我在GitHub上仔细检查过。你觉得错误可能出在哪里呢？

这是snippet/serializers.py的内容：

    from rest_framework import serializers
    from snippets.models import Snippet

    class SnippetSerializer(serializers.Serializer):
        class Meta:
            model = Snippet
            fields = ('id', 'title','code','linenos','language','style')
class SnippetSerializer(serializers.Serializer):
    pk = serializers.Field()  # Note: `Field` is an untyped read-only field.
    title = serializers.CharField(required=False,
                                  max_length=100)
    code = serializers.CharField(widget=widgets.Textarea,
                                 max_length=100000)
    linenos = serializers.BooleanField(required=False)
    language = serializers.ChoiceField(choices=LANGUAGE_CHOICES,
                                       default='python')
    style = serializers.ChoiceField(choices=STYLE_CHOICES,
                                    default='friendly')
def restore_object(self, attrs, instance=None):
        """
        Create or update a new snippet instance, given a dictionary
        of deserialized field values.

        Note that if we don't define this method, then deserializing
        data will simply return a dictionary of items.
        """
        if instance:
            # Update existing instance
            instance.title = attrs.get('title', instance.title)
            instance.code = attrs.get('code', instance.code)
            instance.linenos = attrs.get('linenos', instance.linenos)
            instance.language = attrs.get('language', instance.language)
            instance.style = attrs.get('style', instance.style)
            return instance

        # Create new instance
        return Snippet(**attrs)

这是snippet/urls.py的内容：

from django.conf.urls import patterns, url

urlpatterns = patterns('snippets.views',
    url(r'^snippets/$', 'snippet_list'),
    url(r'^snippets/(?P<pk>[0-9]+)/$', 'snippet_detail'),
)

这是snippet/views.py的内容：

from django.http import HttpResponse
from django.views.decorators.csrf import csrf_exempt
from rest_framework.renderers import JSONRenderer
from rest_framework.parsers import JSONParser
from snippets.models import Snippet
from snippets.serializers import SnippetSerializer

class JSONResponse(HttpResponse):
    """
    An HttpResponse that renders its content into JSON.
    """
    def __init__(self, data, **kwargs):
        content = JSONRenderer().render(data)
        kwargs['content_type'] = 'application/json'
        super(JSONResponse, self).__init__(content, **kwargs)
@csrf_exempt
def snippet_list(request):
    """
    List all code snippets, or create a new snippet.
    """
    if request.method == 'GET':
        snippets = Snippet.objects.all()
        serializer = SnippetSerializer(snippets, many=True)
        return JSONResponse(serializer.data)

    elif request.method == 'POST':
        data = JSONParser().parse(request)
        serializer = SnippetSerializer(data=data)
        if serializer.is_valid():
            serializer.save()
            return JSONResponse(serializer.data, status=201)
        return JSONResponse(serializer.errors, status=400)

@csrf_exempt
def snippet_detail(request, pk):
    """
    Retrieve, update or delete a code snippet.
    """
    try:
        snippet = Snippet.objects.get(pk=pk)
    except Snippet.DoesNotExist:
        return HttpResponse(status=404)

    if request.method == 'GET':
        serializer = SnippetSerializer(snippet)
        return JSONResponse(serializer.data)

    elif request.method == 'PUT':
        data = JSONParser().parse(request)
        serializer = SnippetSerializer(snippet, data=data)
        if serializer.is_valid():
            serializer.save()
            return JSONResponse(serializer.data)
        return JSONResponse(serializer.errors, status=400)

    elif request.method == 'DELETE':
        snippet.delete()
        return HttpResponse(status=204)

Answer 1

对我来说，解决这个问题的关键是文件名。确保文件 serializers 本身没有拼写错误，并且它的名字和代码中使用的一样。

Answer 2

使用 serializers.ModelSerializer：

class SnippetSerializer(serializers.ModelSerializer):

    class Meta:
        model = Snippet
        fields = ('id', 'title','code','linenos','language','style')

这样可以让 DRF（Django REST Framework）知道从指定的模型类 Snippet 中提取字段及其类型，作为序列化器的参数。你现在的版本只在使用 serializers.Serializer。使用基础的 Serializer 类时，你需要为它定义字段变量才能正常工作，像这个例子：

class SnippetSerializer(serializers.Serializer):
    pk = serializers.Field()  # Note: `Field` is an untyped read-only field.
    title = serializers.CharField(required=False,
                                  max_length=100)
    code = serializers.CharField(widget=widgets.Textarea,
                                 max_length=100000)
    linenos = serializers.BooleanField(required=False)
    language = serializers.ChoiceField(choices=LANGUAGE_CHOICES,
                                       default='python')
    style = serializers.ChoiceField(choices=STYLE_CHOICES,
                                    default='friendly')

另外，从 views.py 导入你的视图可能是个更好的做法，像这样：

from django.conf.urls import patterns, url
import views

urlpatterns = patterns('',
    url(r'^snippets/$', views.snippet_list, name='snippet-list'),
    url(r'^snippets/(?P<pk>[0-9]+)/$', views.snippet_detail, name='snippet-detail'),
)

Answer 3

在你的文件 urls.py 中，把 snippets.urls 用引号括起来。

像这样：

url(r'^',include('snippets.urls'))