DRF视图-5个扩展类以及GenericAPIView基类

视图

5个视图扩展类

视图拓展类的作用：

提供了几种后端视图（对数据资源进行曾删改查）处理流程的实现，如果需要编写的视图属于这五种，则视图可以通过继承相应的扩展类来复用代码，减少自己编写的代码量。

这五个扩展类需要搭配GenericAPIView父类，因为五个扩展类的实现需要调用GenericAPIView提供的序列化器与数据库查询的方法。

1）ListModelMixin

列表视图扩展类，提供list(request, *args, **kwargs)方法快速实现列表视图，返回200状态码。

该Mixin的list方法会对数据进行过滤和分页。

源代码：

class ListModelMixin(object):
    """
    List a queryset.
    """
    def list(self, request, *args, **kwargs):
        # 过滤
        queryset = self.filter_queryset(self.get_queryset())
        # 分页
        page = self.paginate_queryset(queryset)
        if page is not None:
            serializer = self.get_serializer(page, many=True)
            return self.get_paginated_response(serializer.data)
        # 序列化
        serializer = self.get_serializer(queryset, many=True)
        return Response(serializer.data)

举例：

from rest_framework.mixins import ListModelMixin

class BookListView(ListModelMixin, GenericAPIView):
    queryset = BookInfo.objects.all()
    serializer_class = BookInfoSerializer

    def get(self, request):
        return self.list(request)

2）CreateModelMixin

创建视图扩展类，提供create(request, *args, **kwargs)方法快速实现创建资源的视图，成功返回201状态码。

如果序列化器对前端发送的数据验证失败，返回400错误。

源代码：

class CreateModelMixin(object):
    """
    Create a model instance.
    """
    def create(self, request, *args, **kwargs):
        # 获取序列化器
        serializer = self.get_serializer(data=request.data)
        # 验证
        serializer.is_valid(raise_exception=True)
        # 保存
        self.perform_create(serializer)
        headers = self.get_success_headers(serializer.data)
        return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers)

    def perform_create(self, serializer):
        serializer.save()

    def get_success_headers(self, data):
        try:
            return {'Location': str(data[api_settings.URL_FIELD_NAME])}
        except (TypeError, KeyError):
            return {}

3）RetrieveModelMixin

详情视图扩展类，提供retrieve(request, *args, **kwargs)方法，可以快速实现返回一个存在的数据对象。

如果存在，返回200， 否则返回404。

源代码：

class RetrieveModelMixin(object):
    """
    Retrieve a model instance.
    """
    def retrieve(self, request, *args, **kwargs):
        # 获取对象，会检查对象的权限
        instance = self.get_object()
        # 序列化
        serializer = self.get_serializer(instance)
        return Response(serializer.data)

举例：

class BookDetailView(RetrieveModelMixin, GenericAPIView):
    queryset = BookInfo.objects.all()
    serializer_class = BookInfoSerializer

    def get(self, request, pk):
        return self.retrieve(request)

4）UpdateModelMixin

更新视图扩展类，提供update(request, *args, **kwargs)方法，可以快速实现更新一个存在的数据对象。

同时也提供partial_update(request, *args, **kwargs)方法，可以实现局部更新。

成功返回200，序列化器校验数据失败时，返回400错误。

源代码：

class UpdateModelMixin(object):
    """
    Update a model instance.
    """
    def update(self, request, *args, **kwargs):
        partial = kwargs.pop('partial', False)
        instance = self.get_object()
        serializer = self.get_serializer(instance, data=request.data, partial=partial)
        serializer.is_valid(raise_exception=True)
        self.perform_update(serializer)

        if getattr(instance, '_prefetched_objects_cache', None):
            # If 'prefetch_related' has been applied to a queryset, we need to
            # forcibly invalidate the prefetch cache on the instance.
            instance._prefetched_objects_cache = {}

        return Response(serializer.data)

    def perform_update(self, serializer):
        serializer.save()

    def partial_update(self, request, *args, **kwargs):
        kwargs['partial'] = True
        return self.update(request, *args, **kwargs)

5）DestroyModelMixin

删除视图扩展类，提供destroy(request, *args, **kwargs)方法，可以快速实现删除一个存在的数据对象。

成功返回204，不存在返回404。

源代码：

class DestroyModelMixin(object):
    """
    Destroy a model instance.
    """
    def destroy(self, request, *args, **kwargs):
        instance = self.get_object()
        self.perform_destroy(instance)
        return Response(status=status.HTTP_204_NO_CONTENT)

    def perform_destroy(self, instance):
        instance.delete()

使用GenericAPIView和视图扩展类，实现api接口，代码：

"""GenericAPIView结合视图扩展类实现api接口"""
from rest_framework.mixins import ListModelMixin,CreateModelMixin
class Students2GenericAPIView(GenericAPIView,ListModelMixin,CreateModelMixin):
    # 本次视图类中要操作的数据[必填]
    queryset = Student.objects.all()
    # 本次视图类中要调用的默认序列化器[玄天]
    serializer_class = StudentModelSerializer

    def get(self, request):
        """获取多个学生信息"""
        return self.list(request)

    def post(self,request):
        """添加学生信息"""
        return self.create(request)

from rest_framework.mixins import RetrieveModelMixin,UpdateModelMixin,DestroyModelMixin
class Student2GenericAPIView(GenericAPIView,RetrieveModelMixin,UpdateModelMixin,DestroyModelMixin):
    queryset = Student.objects.all()

    serializer_class = StudentModelSerializer

    # 在使用GenericAPIView视图获取或操作单个数据时,视图方法中的代表主键的参数最好是pk
    def get(self,request,pk):
        """获取一条数据"""
        return self.retrieve(request,pk)

    def put(self,request,pk):
        """更新一条数据"""
        return self.update(request,pk)

    def delete(self,request,pk):
        """删除一条数据"""
        return self.destroy(request,pk)

GenericAPIView的视图子类

1）CreateAPIView

提供 post 方法

继承自： GenericAPIView、CreateModelMixin

2）ListAPIView

提供 get 方法

继承自：GenericAPIView、ListModelMixin

3）RetrieveAPIView

提供 get 方法

继承自: GenericAPIView、RetrieveModelMixin

4）DestoryAPIView

提供 delete 方法

继承自：GenericAPIView、DestoryModelMixin

5）UpdateAPIView

提供 put 和 patch 方法

继承自：GenericAPIView、UpdateModelMixin

6）RetrieveUpdateAPIView

提供 get、put、patch方法

继承自： GenericAPIView、RetrieveModelMixin、UpdateModelMixin

7）RetrieveUpdateDestoryAPIView

提供 get、put、patch、delete方法

继承自：GenericAPIView、RetrieveModelMixin、UpdateModelMixin、DestoryModelMixin

from rest_framework.generics import ListAPIView,CreateAPIView,RetrieveAPIView,UpdateAPIView,DestroyAPIView,RetrieveUpdateDestroyAPIView

class BookGenerView2(ListAPIView,):
    serializer_class = BookModelSerializer
    queryset = Book.objects.all()

class BookGenerView3(RetrieveAPIView,):
    serializer_class = BookModelSerializer
    queryset = Book.objects.all()