API（三）之Class-based Views

使用基于类的视图重写API

我们首先将根视图重写为基于类的视图。所有这一切都涉及到重构views.py。

from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from django.http import Http404
from rest_framework.views import APIView             #APIView适用于CBV
from rest_framework.response import Response
from rest_framework import status

class SnippetList(APIView):
    """
    List all snippets, or create a new snippet.
    """
    def get(self, request, format=None):
        snippets = Snippet.objects.all()
        serializer = SnippetSerializer(snippets, many=True)
        return Response(serializer.data)

    def post(self, request, format=None):
        serializer = SnippetSerializer(data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

到现在为止还很好。它看起来与以前的情况非常相似，但是在不同的HTTP方法之间有了更好的分离。继续更新views.py。

class SnippetDetail(APIView):
    """
    Retrieve, update or delete a snippet instance.
    """
    def get_object(self, pk):
        try:
            return Snippet.objects.get(pk=pk)
        except Snippet.DoesNotExist:
            raise Http404

    def get(self, request, pk, format=None):
        snippet = self.get_object(pk)
        serializer = SnippetSerializer(snippet)
        return Response(serializer.data)

    def put(self, request, pk, format=None):
        snippet = self.get_object(pk)
        serializer = SnippetSerializer(snippet, data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

    def delete(self, request, pk, format=None):
        snippet = self.get_object(pk)
        snippet.delete()
        return Response(status=status.HTTP_204_NO_CONTENT)

看起来不错。它现在仍然非常类似于基于函数的视图。

我们还需要重构urls.py。

from django.conf.urls import url
from rest_framework.urlpatterns import format_suffix_patterns
from snippets import views

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

urlpatterns = format_suffix_patterns(urlpatterns)

好了，如果运行开发服务器，那么应​​该像以前那样工作。

Using mixins

使用基于类的视图的优势之一是 that it allows us to easily compose reusable bits of behaviour.

到目前为止，我们使用的创建/检索/更新/删除(create/retrieve/update/delete)操作将与我们创建的任何支持模型的API视图非常相似。这些常见的行为是在REST框架的mixin类中实现的。

我们来看看我们如何通过使用mixin类编写视图。还是重构views.py。

from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from rest_framework import mixins
from rest_framework import generics

class SnippetList(mixins.ListModelMixin,
                  mixins.CreateModelMixin,
                  generics.GenericAPIView):
    queryset = Snippet.objects.all()                 #queryset是GenericAPIView的属性。
    serializer_class = SnippetSerializer             #serializer_class是GenericAPIView的属性。

    def get(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)   #list是ListModelMixin的方法。

    def post(self, request, *args, **kwargs):
        return self.create(request, *args, **kwargs) #create是CreateModelMixin的方法。

我们会花点时间仔细检查这里发生的情况。我们正在使用GenericAPIView创建视图，并把它加到ListModelMixin和CreateModelMixin中。

基类提供核心功能，而mixin类提供.list()和.create()操作。我们再明确绑定get和post方法，以适合这些操作。

class SnippetDetail(mixins.RetrieveModelMixin,
                    mixins.UpdateModelMixin,
                    mixins.DestroyModelMixin,
                    generics.GenericAPIView):
    queryset = Snippet.objects.all()
    serializer_class = SnippetSerializer

    def get(self, request, *args, **kwargs):
        return self.retrieve(request, *args, **kwargs)   #retrieve是RetrieveModelMixin的方法。

    def put(self, request, *args, **kwargs):
        return self.update(request, *args, **kwargs)     #update是UpdateModelMixin的方法。

    def delete(self, request, *args, **kwargs):
        return self.destroy(request, *args, **kwargs)    #destroy是DestroyModelMixin的方法。

Pretty similar. Again we're using the GenericAPIView class to provide the core functionality, and adding in mixins to provide the .retrieve(), .update() and .destroy() actions.

Using generic class-based views

我们使用mixin类重写了这些视图，使用的代码比以前少一些，但我们可以进一步。REST框架提供了一组已经混合的通用视图，我们可以使用它来让views.py模块更简化。 

from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from rest_framework import generics

class SnippetList(generics.ListCreateAPIView):                 #get封装到ListCreateAPIView中了。
    queryset = Snippet.objects.all()
    serializer_class = SnippetSerializer


class SnippetDetail(generics.RetrieveUpdateDestroyAPIView):    #get、put、delete都封装到RetrieveUpdateDestroyAPIView中了。
    queryset = Snippet.objects.all()
    serializer_class = SnippetSerializer

 更简洁了！