Rest framework 学习（3）基于类的视图（CBV）

首页，回顾一下实现接口的两类方法FBV和CBV：

基于函数的视图叫做FBV，基于类的视图叫做CBV。

在API中使用CBV的优点：

1.提高了代码的复用性（keep our code DRY），可以使用面向对象的技术，比如Mixin（多继承）

2.可以用不同的函数针对不同的HTTP方法处理，而不是通过很多if判断，提高代码可读性

一，类试于函数的类视图形式：

这种模式通过APIView实现了对不同的HTTP方法分离处理，算很规范了。

from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from django.http import Http404
from rest_framework.views import APIView
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)


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)

然乎修改urls.py 使其基于类的视图

from django.urls import path
from rest_framework.urlpatterns import format_suffix_patterns
from snippets import views

urlpatterns = [
    path('snippets/', views.SnippetList.as_view()),
    path('snippets/<int:pk>/', views.SnippetDetail.as_view()),
]

urlpatterns = format_suffix_patterns(urlpatterns)

二,使用MiXin的类视图

在这部分，MiXin是能丰富其他类能力的工具类，这里主要使用：

ListModelMixin: self.list()   # 换回 queryset list

CreateModelMixin: self.create() 

RetrieveModelMixin: self.retrieve()   # 检索 

UpdateModelMixin: self.update()

DestroyModelMixin: self.destroy()

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()
    serializer_class = SnippetSerializer

    def get(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)

    def post(self, request, *args, **kwargs):
        return self.create(request, *args, **kwargs)

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)

    def put(self, request, *args, **kwargs):
        return self.update(request, *args, **kwargs)

    def delete(self, request, *args, **kwargs):
        return self.destroy(request, *args, **kwargs)

三， 基于类的通用视图

由于Rest framework 已经封装了对MiXin的混合集成了。所以我们可以更进一步简化代码

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


class SnippetList(generics.ListCreateAPIView):
    queryset = Snippet.objects.all()
    serializer_class = SnippetSerializer


class SnippetDetail(generics.RetrieveUpdateDestroyAPIView):
    queryset = Snippet.objects.all()
    serializer_class = SnippetSerializer

总结：

CBV是我们优先考虑的API的设计方式。

从由自己去实现get,post的内部细节，到使用MiXin协助简化代码，到最后的直接调用集成的rest_framework.generics，不断提高开发效率，也减少了出错的可能。