【Django】REST_Framework框架——Mixin类和GenericAPIView中的视图子类源码解析

一、Mixin类

提供了几种后端视图（对数据资源进行增删改查）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通用视图基类来开发业务接口

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，如果不重写过滤和分页的方法是不会进行过滤和分页的。

源码简化

class ListModelMixin:
	def list(self,request,*args,**kwargs):
	      queryset=self.get_queryset()
	      serializer=self.get_serializer(instance=queryset,many=True)
	      return Response(serializer.data)
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源码

class ListModelMixin:
    """
    List a queryset.
    """
    def list(self, request, *args, **kwargs):
        queryset = self.filter_queryset(self.get_queryset())

        page = self.paginate_queryset(queryset)
        if page is not None:
            serializer = self.get_serializer(page, many=True)
            return self.get_paginated_response(serializer.data)

        serializer = self.get_serializer(queryset, many=True)
        return Response(serializer.data)
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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；所以要对反序列化输入字段要进行验证，校验不通过提供指定的报错。

源码简化

class CreateModelMixin:
	def create(self,request,*args,**kwargs):
	      serializer=self.get_serializer(data=request.data)
	      serializer.is_valid(raise_exception=True)
	      serializer.save()
	      return Response(serializer.data)
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源码

class CreateModelMixin:
    """
    Create a model instance.
    """
    def create(self, request, *args, **kwargs):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        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 {}
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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。

源码

class RetrieveModelMixin:
	def retrieve(self,request,*args,**kwargs):
	      instance=self.get_object()
	      serializer=ProjectsSerializer(instance=instance)
	      return Response(serializer.data)
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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。

源码简化

class UpdateModelMixin:
	def update(self,request,*args,**kwargs):
	     obj=self.get_object()
	     serializer=ProjectsSerializer(instance=obj,data=request.data)
	     serializer.is_valid(raise_exception=True)
	     serializer.save()
	     return Response(serializer.data)
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源码

class UpdateModelMixin:
    """
    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)
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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。

源码简化

class DestroyModelMixin
	def destroy(self,request,*args,**kwargs):
	     obj=self.get_object()
	     obj.delete()
	     return Response({'msg':'删除数据成功'},status=204)
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源码

class DestroyModelMixin:
    """
    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()
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二、GenericAPIView的视图子类

1、CreateAPIView

提供post方法
继承关系：CreateModelMixin、GenericAPIView
使用：基本属性定义：queryset、serializer_class

class CreateAPIView(mixins.CreateModelMixin,
                    GenericAPIView):
    """
    Concrete view for creating a model instance.
    """
    def post(self, request, *args, **kwargs):
        return self.create(request, *args, **kwargs)
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2、ListAPIView

提供get方法
继承关系：ListModelMixin、GenericAPIView
使用：基本属性定义：queryset、serializer_class

class ListAPIView(mixins.ListModelMixin,
                  GenericAPIView):
    """
    Concrete view for listing a queryset.
    """
    def get(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)
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3、RetrieveAPIView

提供get方法
继承关系：RetrieveModelMixin、GenericAPIView
使用：基本属性定义：queryset、serializer_class

class RetrieveAPIView(mixins.RetrieveModelMixin,
                      GenericAPIView):
    """
    Concrete view for retrieving a model instance.
    """
    def get(self, request, *args, **kwargs):
        return self.retrieve(request, *args, **kwargs)
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4、UpdateAPIView

提供put、patch方法
继承关系：UpdateModelMixin、GenericAPIView
使用：基本属性定义：queryset、serializer_class

class UpdateAPIView(mixins.UpdateModelMixin,
                    GenericAPIView):
    """
    Concrete view for updating a model instance.
    """
    def put(self, request, *args, **kwargs):
        return self.update(request, *args, **kwargs)

    def patch(self, request, *args, **kwargs):
        return self.partial_update(request, *args, **kwargs)
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5、DestoryAPIView

提供delete方法
继承关系：DestoryModelMixin、GenericAPIView
使用：基本属性定义：queryset、serializer_class

class DestroyAPIView(mixins.DestroyModelMixin,
                     GenericAPIView):
    """
    Concrete view for deleting a model instance.
    """
    def delete(self, request, *args, **kwargs):
        return self.destroy(request, *args, **kwargs)
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6、ListCreateAPIView

提供get、post方法
继承关系：ListModelMixin、CreateModelMixin、GenericAPIView
使用：基本属性定义：queryset、serializer_class

class ListCreateAPIView(mixins.ListModelMixin,
                        mixins.CreateModelMixin,
                        GenericAPIView):
    """
    Concrete view for listing a queryset or creating a model instance.
    """
    def get(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)

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

提供get、put、patch方法
继承关系：RetrieveModelMixin、UpdateModelMixin、GenericAPIView
使用：基本属性定义：queryset、serializer_class

class RetrieveUpdateAPIView(mixins.RetrieveModelMixin,
                            mixins.UpdateModelMixin,
                            GenericAPIView):
    """
    Concrete view for retrieving, updating a model instance.
    """
    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 patch(self, request, *args, **kwargs):
        return self.partial_update(request, *args`
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8、RetrieveDestoryAPIView

提供get、delete方法
继承关系：RetrieveModelMixin、DestoryModelMixin、GenericAPIView
使用：基本属性定义：queryset、serializer_class

class RetrieveDestroyAPIView(mixins.RetrieveModelMixin,
                             mixins.DestroyModelMixin,
                             GenericAPIView):
    """
    Concrete view for retrieving or deleting a model instance.
    """
    def get(self, request, *args, **kwargs):
        return self.retrieve(request, *args, **kwargs)

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

提供get、put、patch、delete方法
继承关系：RetrieveModelMixin、UpdateModelMixin、DestoryModelMixin、GenericAPIView
使用：基本属性定义：queryset、serializer_class

class RetrieveUpdateDestroyAPIView(mixins.RetrieveModelMixin,
                                   mixins.UpdateModelMixin,
                                   mixins.DestroyModelMixin,
                                   GenericAPIView):
    """
    Concrete view for retrieving, updating or deleting a model instance.
    """
    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 patch(self, request, *args, **kwargs):
        return self.partial_update(request, *args, **kwargs)

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

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