Django REST Framework(DRF)_第二篇

视图和路由

视图封装

第一次封装

上一篇最后我们对书籍表做了增删改查,那么如果现在我们有几十上百张表需要这样做呢?我们知道类的特性有封装,因此我们可以尝试进行封装下.

from rest_framework.views import APIView
  from rest_framework.response import Response
  
  from .models import Book
  from .modelSerializers import BookModelSerializer
  
  
  class GenericAPIView(APIView):
      queryset = None
      serializer_class = None
  
      def get_queryset(self):
          return self.queryset.all()
  
      def get_serializer(self, *args, **kwargs):
          return self.serializer_class(*args, **kwargs)
  
  
  class ListModelMixin(object):
      # 这个就是把get方法抽离了出来,变成了list方法
      def list(self, request, *args, **kwargs):
          queryset = self.get_queryset()
          serializer_data = self.get_serializer(queryset, many=True)
          return Response(serializer_data.data)
  
  
  class CreateModelMixin(object):
      def create(self,  request, *args, **kwargs):
          ser_obj = self.get_serializer(data=request.data)
          if ser_obj.is_valid():
              ser_obj.save()
              return Response(ser_obj.validated_data)
          return Response(ser_obj.errors)
  
  
  class RetrieveModelMixin(object):
      def retrieve(self, request, id, *args, **kwargs):
          book_obj = self.get_queryset().filter(pk=id).first()
          ser_obj = self.get_serializer(book_obj)
          return Response(ser_obj.data)
  
  
  class UpdateModelMixin(object):
      def update(self, request, id, *args, **kwargs):
          book_obj = self.get_queryset().filter(pk=id).first()
          ser_obj = self.get_serializer(instance=book_obj, data=request.data, partial=True)
          if ser_obj.is_valid():
              ser_obj.save()
              return Response(ser_obj.validated_data)
          return Response(ser_obj.errors)
  
  
  class DestroyModeMixin(object):
      def destroy(self, request, id , *args, **kwargs):
          book_obj = self.get_queryset().filter(id=id).first()
          if not book_obj:
              return Response("要删除的对象不存在")
          book_obj.delete()
          return Response("")
  
  
  class ListCreateAPIView(GenericAPIView, ListModelMixin, CreateModelMixin):
      pass
  
  
  class RetrieveUpdateDestroyAPIView(GenericAPIView, RetrieveModelMixin, UpdateModelMixin, DestroyModeMixin):
      pass
  
  
  class BookView(ListCreateAPIView):
      """书籍相关视图"""
      queryset = Book.objects
      serializer_class = BookModelSerializer
  
      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 BookEditView(RetrieveUpdateDestroyAPIView):
      queryset = Book.objects
      serializer_class = BookModelSerializer
  
      def get(self, request, id, *args, **kwargs):
          return self.retrieve(request, id, *args, **kwargs)
  
      def put(self, request,  id, *args, **kwargs):
          return self.update(request, id, *args, **kwargs)
  
      def delete(self, request, id, *args, **kwargs):
          return self.destroy(request, id, *args, **kwargs)

从上面我们可以知道,我们发现视图中就只有query和ModelSerializer每个方法不一样,因此,我们先定义了一个GenericAPIView,该方法就是专门获取query和ModelSerializer.再接着就是将get全部/get单条/post/put/delete方法分别再次封装到不同类中的方法中,这样在写多个表时只需要调用方法即可,但是此时你会发现继承的类有点长,因此又封装了两个类专门继承多个类,这样我们再写就只需要继承一个类了,你看这样是不是变得更简单了,我们必须学习这种封装的思想,使得自己代码更加简洁,复用性更高.

二次最终封装

上面封装似乎已经很好了,但是人总是贪婪的,上面是不是定义了两个视图针对不同操作(BookView和BookEditView),那我们想能不能只定义一个视图就完成呢?此时我们去看一下rest_framework提供的源码

在这里先被备注下rest_framework给我们的几个视图相关的类

from rest_framework import views        # 里面主要是有APIView
from rest_framework import viewsets     # ModelViewSet封装,继承mixins下的各个类
from rest_framework import generics     # GenericAPIView,CreateAPIView等封装
from rest_framework import mixins       # list,create,update等方法具体实现

因为我们需要合并视图,所以我们需要在as_view()时出入对应关系的参数,所以我们看下viewsets下的ViewSetMixin类, from rest_framework.viewsets import ViewSetMixin.

从ViewSetMixin中我们可以知道,重写了as_view()方法,并且将参数传给了action,这里我只拿出了一些需要的代码进行说明下.

def as_view(cls, actions=None, **initkwargs):
    # actions = {"get": "list", "post": "create"}
    def view(request, *args, **kwargs):
          for method, action in actions.items():
                # method = get, action = list
                handler = getattr(self, action)
                # 这里就将self.get = self.list,所以之后get请求就会去找list方法
                setattr(self, method, handler)

所以注意下,只有继承了ViewSetMixin路由才可以传参,前面说完了,我们来再次封装下代码:

views下就变成了

class ModelViewSet(ViewSetMixin, ListCreateAPIView, RetrieveUpdateDestroyAPIView):
    pass


class BooksView(ModelViewSet):
    queryset = Book.objects
    serializer_class = BookModelSerializer

urls下变成

path('books', views.BooksView.as_view({"get": "list", "post": "create"})),
re_path('book/(?P<id>\d+)', views.BooksView.as_view({"get": "retrieve", "patch": "update", "delete": "destroy"})),

其实我们辗转了大半天,人家早就给我们封装好了,views下我们啥都不用写,就只需要继承人家封装好的就可以了,就下面几行代码即可

DRF视图最终写法

from rest_framework import viewsets 
class BooksView(viewsets.ModelViewSet):
    queryset = Book.objects
    serializer_class = BookModelSerializer

但是urls那里不能写id了,只能写pk

path('books', views.BooksView.as_view({"get": "list", "post": "create"})),
re_path('book/(?P<pk>\d+)', views.BooksView.as_view({"get": "retrieve", "patch": "update", "delete": "destroy"})),

DRF路由

思考下,如果我们要写几十张表的路由,那岂不是又要每个路由传一堆一样的参数?别怕,DRF又帮我们搞定了,我们只需要按照下面的方式写即可
```
from rest_framework.routers import DefaultRouter

# 实例化DefaultRouter
router = DefaultRouter()
# 注册路由以及视图
router.register(r"book", views.BooksView)

# 将路由url加入到urlpatterns
urlpatterns += router.urls
```
该方法虽然简洁快速,但也会暴露很多路由接口,视情况选择使用.