drf之视图扩展类(混入类)

### 1.2.2 5个视图扩展类 - 也叫混入类。

作用：
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，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,CreateModelMixin
class StudentMixinAPIView(GenericAPIView,ListModelMixin,CreateModelMixin):
    serializer_class = StudentModelSerializer
    queryset = Student.objects
    def get(self,request,*args,**kwargs):
        """获取所有模型信息"""
        return self.list(request,*args,**kwargs)

#### 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 {}

视图代码

from rest_framework.mixins import ListModelMixin,CreateModelMixin
class StudentMixinAPIView(GenericAPIView,ListModelMixin,CreateModelMixin):
    serializer_class = StudentModelSerializer
    queryset = Student.objects
    def get(self,request,*args,**kwargs):
        """获取所有模型信息"""
        return self.list(request,*args,**kwargs)

    def post(self,request):
        """添加一个模型信息"""
        return self.create(request)

#### 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)

视图代码：

from rest_framework.mixins import RetrieveModelMixin,UpdateModelMixin,DestroyModelMixin
class Student1MixinAPIView(GenericAPIView,RetrieveModelMixin,UpdateModelMixin,DestroyModelMixin):
    serializer_class = StudentModelSerializer
    queryset = Student.objects
    def get(self,request,pk):
        """获取一个模型信息"""
        return self.retrieve(request,pk)

#### 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)

视图代码：

from rest_framework.mixins import RetrieveModelMixin,UpdateModelMixin,DestroyModelMixin
class Student1MixinAPIView(GenericAPIView,RetrieveModelMixin,UpdateModelMixin,DestroyModelMixin):
    serializer_class = StudentModelSerializer
    queryset = Student.objects
    def get(self,request,pk):
        """获取一个模型信息"""
        return self.retrieve(request,pk)

    def put(self,request,pk):
        """更新一个模型信息"""
        return self.update(request,pk)

#### 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()

视图代码：

from rest_framework.mixins import RetrieveModelMixin,UpdateModelMixin,DestroyModelMixin
class Student1MixinAPIView(GenericAPIView,RetrieveModelMixin,UpdateModelMixin,DestroyModelMixin):
    serializer_class = StudentModelSerializer
    queryset = Student.objects
    def get(self,request,pk):
        """获取一个模型信息"""
        return self.retrieve(request,pk)

    def put(self,request,pk):
        """更新一个模型信息"""
        return self.update(request,pk)

    def delete(self,request,pk):
        """删除一个模型信息"""
        return self.destroy(request,pk)

整体代码，使用GenericAPIView结合视图扩展类，实现5个基本api接口，视图代码：

"""
使用drf内置的模型扩展类[混入类]结合GenericAPIView实现通用视图方法的简写操作
from rest_framework.mixins import ListModelMixin   获取多条数据，返回响应结果    list
from rest_framework.mixins import CreateModelMixin 添加一条数据，返回响应结果    create
from rest_framework.mixins import RetrieveModelMixin 获取一条数据，返回响应结果  retrieve
from rest_framework.mixins import UpdateModelMixin 更新一条数据，返回响应结果    update(更新全部字段)和partial_update(更新单个或部分字段，例如修改密码，修改头像)
from rest_framework.mixins import DestroyModelMixin 删除一条数据，返回响应结果   destroy
"""
from rest_framework.mixins import ListModelMixin, CreateModelMixin


class StudentMixinView(GenericAPIView, ListModelMixin, CreateModelMixin):
    queryset = Student.objects.all()
    serializer_class = StudentModelSerializer
    def get(self,request):
        """获取所有数据"""
        return self.list(request)

    def post(self,request):
        """添加一条数据"""
        return self.create(request)


from rest_framework.mixins import RetrieveModelMixin, UpdateModelMixin, DestroyModelMixin

class StudentInfoMixinView(GenericAPIView, RetrieveModelMixin, UpdateModelMixin, DestroyModelMixin):
    queryset = Student.objects.all()
    serializer_class = StudentModelSerializer

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

    def put(self,request, pk):
        return self.update(request, pk=pk)

    def delete(self,request, pk):
        return self.destroy(request, pk=pk)

序列化器，代码：

from rest_framework import serializers
from stuapi.models import Student


class StudentModelSerializer(serializers.ModelSerializer):
    class Meta:
        model = Student
        fields = "__all__"
        extra_kwargs = {
            "age": {
                "max_value": 25,
                "error_messages": {
                    "max_value": "年龄不能超过25岁！",
                }
            }
        }

路由代码：

from django.urls import path, re_path
from . import views

urlpatterns = [
    # APIView
    path("students/", views.StudentAPIView.as_view()),
    re_path("^students/(?P<pk>\d+)/$", views.StudentInfoAPIView.as_view()),

    # GenericAPIView
    path("students2/", views.StudentGenericAPIView.as_view()),
    re_path("^students2/(?P<pk>\d+)/$", views.StudentInfoGenericAPIView.as_view()),

    # GenericAPIView + mixins
    path("students3/", views.StudentMixinView.as_view()),
    re_path("^students3/(?P<pk>\d+)/$", views.StudentInfoMixinView.as_view()),
]

### 1.2.3 9个视图子类

#### 1）CreateAPIView

提供了post方法，内部调用了create方法

继承自： GenericAPIView、CreateModelMixin

#### 2）ListAPIView

提供了get方法，内部调用了list方法

继承自：GenericAPIView、ListModelMixin

#### 3）RetrieveAPIView

提供了get方法，内部调用了retrieve方法

继承自: GenericAPIView、RetrieveModelMixin

#### 4）DestoryAPIView

提供了delete方法，内部调用了destory方法

继承自：GenericAPIView、DestoryModelMixin

#### 5）UpdateAPIView

提供了put和patch方法，内部调用了update和partial_update方法

继承自：GenericAPIView、UpdateModelMixin

#### 6）ListCreateAPIView

提供了get和post方法，内部调用了list和create方法

继承自：GenericAPIView、ListModelMixin、CreateModelMixin

#### 7）RetrieveUpdateAPIView

提供 get、put、patch方法

继承自： GenericAPIView、RetrieveModelMixin、UpdateModelMixin

#### 8）RetrieveDestoryAPIView

提供 get、delete方法

继承自：GenericAPIView、RetrieveModelMixin、DestoryModelMixin

#### 9）RetrieveUpdateDestoryAPIView

提供 get、put、patch、delete方法

继承自：GenericAPIView、RetrieveModelMixin、UpdateModelMixin、DestoryModelMixin

视图代码：

"""
上面的接口代码还可以继续更加的精简，drf在使用GenericAPIView和Mixins进行组合以后，还提供了视图子类。
视图子类是通用视图类 和 模型扩展类 的子类，提供了各种的视图方法调用mixins操作
    ListAPIView = GenericAPIView + ListModelMixin         获取多条数据的视图方法
    CreateAPIView = GenericAPIView + CreateModelMixin     添加一条数据的视图方法
    RetrieveAPIView = GenericAPIView + RetrieveModelMixin 获取一条数据的视图方法
    UpdateAPIView = GenericAPIView + UpdateModelMixin     更新一条数据的视图方法
    DestroyAPIView = GenericAPIView + DestroyModelMixin   删除一条数据的视图方法
组合视图子类
    ListCreateAPIView = ListAPIView + CreateAPIView
    RetrieveUpdateAPIView = RetrieveAPIView + UpdateAPIView
    RetrieveDestroyAPIView = RetrieveAPIView + DestroyAPIView
    RetrieveUpdateDestroyAPIView = RetrieveAPIView + UpdateAPIView + DestroyAPIView
"""

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


# class StudentView(ListAPIView, CreateAPIView):
class StudentView(ListCreateAPIView):
    queryset = Student.objects.all()
    serializer_class = StudentModelSerializer


# class StudentInfoView(RetrieveAPIView, UpdateAPIView, DestroyAPIView):
# class StudentInfoView(RetrieveUpdateAPIView, DestroyAPIView):
class StudentInfoView(RetrieveUpdateDestroyAPIView):
    queryset = Student.objects.all()
    serializer_class = StudentModelSerializer

序列化器，代码：

from rest_framework import serializers
from stuapi.models import Student


class StudentModelSerializer(serializers.ModelSerializer):
    class Meta:
        model = Student
        fields = "__all__"
        extra_kwargs = {
            "age": {
                "max_value": 25,
                "error_messages": {
                    "max_value": "年龄不能超过25岁！",
                }
            }
        }

路由，代码：

from django.urls import path, re_path
from . import views

urlpatterns = [
    # APIView
    path("students/", views.StudentAPIView.as_view()),
    re_path("^students/(?P<pk>\d+)/$", views.StudentInfoAPIView.as_view()),

    # GenericAPIView
    path("students2/", views.StudentGenericAPIView.as_view()),
    re_path("^students2/(?P<pk>\d+)/$", views.StudentInfoGenericAPIView.as_view()),

    # GenericAPIView + mixins
    path("students3/", views.StudentMixinView.as_view()),
    re_path("^students3/(?P<pk>\d+)/$", views.StudentInfoMixinView.as_view()),

    # 视图子类
    path("students4/", views.StudentView.as_view()),
    re_path("^students4/(?P<pk>\d+)/$", views.StudentInfoView.as_view()),
]