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()