Django REST 框架详解 06 | 视图家族 Generics 与 Viewsets

一、Generics：工具视图

generics 是工具视图，可以实现极简化接口编写操作。

工具视图都是 GenericAPIView 的子类，不同的子类继承不同工具类，重写请求方法。

1.群查与单增：ListCreateAPIView

查看源码

# 继承了视图基类 GenericAPIView，工具类 ListModelMixin，CreateModelMixin实现群查和单增
class ListCreateAPIView(mixins.ListModelMixin,
                        mixins.CreateModelMixin,
                        GenericAPIView):
    """
    Concrete view for listing a queryset or creating a model instance.
    """
    # 群查
    def get(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)
	
    # 单增
    def post(self, request, *args, **kwargs):
        # 继承了视图基类 GenericAPIView，工具类 ListModelMixin，CreateModelMixin实现群查和单增
class ListCreateAPIView(mixins.ListModelMixin,
                        mixins.CreateModelMixin,
                        GenericAPIView):
    """
    Concrete view for listing a queryset or creating a model instance.
    """
    # 群查
    def get(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)
	
    # 单增
    def post(self, request, *args, **kwargs):
        return self.create(request, *args, **kwargs)

代码实现

urls.py

from django.conf.urls import url, include

from api import views

urlpatterns = [
	url(r'^v4/books/$', views.BookListCreateView.as_view()),
    url(from django.conf.urls import url, include

from api import views

urlpatterns = [
	url(r'^v4/books/$', views.BookListCreateView.as_view()),
    url(r'^v4/books/(?P.*)/$', views.BookListCreateView.as_view()),
]

工具视图的功能如果满足需求，只需要继承工具视图，添加 queryset，serializer_class

views.py

class BookListCreateView(ListCreateAPIView):
    queryset = models.Book.objects.filter(is_delete=class BookListCreateView(ListCreateAPIView):
    queryset = models.Book.objects.filter(is_delete=False)
    serializer_class = serializers.BookModelSerializer

测试接口

群查

单增

入库成功

其他方法

根据上述源码分析与示例和下面的图示，我们可以很容易知道这些类的功能和用法

2.添加其他接口

代码实现

# 需要什么接口，直接继承就行
# 比如我们在群查，单增的基础上，添加单改接口
class BookListCreateView(ListCreateAPIView, UpdateAPIView):
    queryset = models.Book.objects.filter(is_delete=# 需要什么接口，直接继承就行
# 比如我们在群查，单增的基础上，添加单改接口
class BookListCreateView(ListCreateAPIView, UpdateAPIView):
    queryset = models.Book.objects.filter(is_delete=False)
    serializer_class = serializers.BookModelSerializer

接口测试

修改成功

3.后续问题

但是上述虽然可以实现简单接口，但是有时候需求会很复杂。

比如，来自前端用户的数据格式并不是和我们规定的一样，有可能传来空值，错误字符等等。这就需要对 request.data 进行过滤，尤其是在入库的时候。

另外，如果数据有误，DRF 并不知道你的字段是哪出的问题，所以抛异常是只会是数据错误。我们需要对每个字段的每种错误类型给出对应的返回值。

可以在 UpdateModelMixin 源码中看到，request.data 并没有进行过滤。

class UpdateModelMixin:
   
    def update(self, request, *args, **kwargs):
        partial = kwargs.pop('partial', False)
        instance = self.get_object()
        # request.data 并没有进行过滤
        serializer = self.get_serializer(instance, data=request.data, partial=partial)
        class UpdateModelMixin:
   
    def update(self, request, *args, **kwargs):
        partial = kwargs.pop('partial', False)
        instance = self.get_object()
        # request.data 并没有进行过滤
        serializer = self.get_serializer(instance, data=request.data, partial=partial)
        # ...

二、Viewsets：视图集

1.简单使用

DRF 提供了 Viewsets.py 视图集，再次封装之前的操作。最主要的是，可以通过设置 请求-函数 映射关系，来将请求方式与原有方法或自定义方法对应执行。

查看源码

发现没有提供实际的方法

class GenericViewSet(ViewSetMixin, generics.GenericAPIView):
    """
    The GenericViewSet class does not provide any actions by default,
    but does include the base set of generic view behavior, such as
    the `get_object` and `get_queryset` methods.
    """
    class GenericViewSet(ViewSetMixin, generics.GenericAPIView):
    """
    The GenericViewSet class does not provide any actions by default,
    but does include the base set of generic view behavior, such as
    the `get_object` and `get_queryset` methods.
    """
    pass

但是看到它继承了 ViewSetMixin，GenericAPIView

查看 ViewSetMixin 类的 as_view 方法

GenericViewSet 和 ViewSet 都继承了 ViewSetMixin，as_view 可以配置 请求-函数 映射

比如view = MyViewSet.as_view({'get': 'list', 'post': 'create'})

class ViewSetMixin:

    @classonlymethod
    def as_view(cls, actions=None, **initkwargs):
        #...

        def view(request, *args, **kwargs):
            # 这里 cls 去解析前边例子中的 {'get': 'list', 'post': 'create'}
            self = cls(**initkwargs)
            self.action_map = actions

            # methods拿到请求方法，比如get
            for method, action in actions.items():
                handler = getattr(self, action)
                # 映射method get到执行函数handler list
                setattr(self, method, handler)

            if hasattr(self, 'get') and not hasattr(self, 'head'):
                self.head = self.get

            self.request = request
            self.args = args
            self.kwargs = kwargs

            # 继承 APIView 中的 dispatch 进行分发
            return self.dispatch(request, *args, **kwargs)
		
        class ViewSetMixin:

    @classonlymethod
    def as_view(cls, actions=None, **initkwargs):
        #...

        def view(request, *args, **kwargs):
            # 这里 cls 去解析前边例子中的 {'get': 'list', 'post': 'create'}
            self = cls(**initkwargs)
            self.action_map = actions

            # methods拿到请求方法，比如get
            for method, action in actions.items():
                handler = getattr(self, action)
                # 映射method get到执行函数handler list
                setattr(self, method, handler)

            if hasattr(self, 'get') and not hasattr(self, 'head'):
                self.head = self.get

            self.request = request
            self.args = args
            self.kwargs = kwargs

            # 继承 APIView 中的 dispatch 进行分发
            return self.dispatch(request, *args, **kwargs)
		
        # ...

代码实现

这样的好处是，各种需求的接口的请求方式都可以用不同函数定义返回值。比如十大接口对应十个函数，分别码代码。

views.py

class BookGenericViewSet(RetrieveModelMixin, ListModelMixin, GenericViewSet):
    queryset = models.Book.objects.filter(is_delete=False)
    serializer_class = serializers.BookModelSerializer

    def get_list(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)

    def get_obj(self, request, *args, **kwargs):
        class BookGenericViewSet(RetrieveModelMixin, ListModelMixin, GenericViewSet):
    queryset = models.Book.objects.filter(is_delete=False)
    serializer_class = serializers.BookModelSerializer

    def get_list(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)

    def get_obj(self, request, *args, **kwargs):
        return self.retrieve(request, *args, **kwargs)

urls.py

from django.contrib import admin
from django.urls import path
from django.conf.urls import url, include
from django.views.static import serve
from django.conf import settings

from api import views

urlpatterns = [
    # ...
    url(r'^v5/books/$', views.BookGenericViewSet.as_view({'get':'get_list'})),
    url(r'^v5/books/(?P<pk>.*)/$', views.BookGenericViewSet.as_view({'get':from django.contrib import admin
from django.urls import path
from django.conf.urls import url, include
from django.views.static import serve
from django.conf import settings

from api import views

urlpatterns = [
    # ...
    url(r'^v5/books/$', views.BookGenericViewSet.as_view({'get':'get_list'})),
    url(r'^v5/books/(?P<pk>.*)/$', views.BookGenericViewSet.as_view({'get':'get_obj'})),
]

2.ModelViewSet：最全的封装类

查看源码

class ModelViewSet(mixins.CreateModelMixin,
                   mixins.RetrieveModelMixin,
                   mixins.UpdateModelMixin,
                   mixins.DestroyModelMixin,
                   mixins.ListModelMixin,
                   GenericViewSet):
    """
    A viewset that provides default `create()`, `retrieve()`, `update()`,
    `partial_update()`, `destroy()` and `list()` actions.
    """
    class ModelViewSet(mixins.CreateModelMixin,
                   mixins.RetrieveModelMixin,
                   mixins.UpdateModelMixin,
                   mixins.DestroyModelMixin,
                   mixins.ListModelMixin,
                   GenericViewSet):
    """
    A viewset that provides default `create()`, `retrieve()`, `update()`,
    `partial_update()`, `destroy()` and `list()` actions.
    """
    pass

代码实现

views.py

# 继承 ModelViewset 会直接拥有六大接口：单查，群查，单增，单删，单整体改，单局部改
# 需要注意：Destroy 需要重写
class BookModelViewSet(ModelViewSet):
    queryset = models.Book.objects.filter(is_delete=False)
    serializer_class = serializers.BookModelSerializer

    # 删除操作
    def destroy(self, request, *args, **kwargs):
        instance = self.get_object() # type: models.Book
        if not instance:
            return APIResponse(1, "Delete fail")
        instance.is_delete = True
        instance.save()
        return APIResponse(1, # 继承 ModelViewset 会直接拥有六大接口：单查，群查，单增，单删，单整体改，单局部改
# 需要注意：Destroy 需要重写
class BookModelViewSet(ModelViewSet):
    queryset = models.Book.objects.filter(is_delete=False)
    serializer_class = serializers.BookModelSerializer

    # 删除操作
    def destroy(self, request, *args, **kwargs):
        instance = self.get_object() # type: models.Book
        if not instance:
            return APIResponse(1, "Delete fail")
        instance.is_delete = True
        instance.save()
        return APIResponse(1, "Delete successful")

urls.py

from django.conf.urls import url

from api import views

urlpatterns = [
    url(r'^v6/books/$', views.BookModelViewSet.as_view({'get':'list', 'post':'create'})),
    url(r'^v6/books/(?P<pk>.*)/$', views.BookModelViewSet.as_view({'get': 'retrieve', 'post':'create', 'put': 'update', 'patch': 'partial_update', 'delete': from django.conf.urls import url

from api import views

urlpatterns = [
    url(r'^v6/books/$', views.BookModelViewSet.as_view({'get':'list', 'post':'create'})),
    url(r'^v6/books/(?P<pk>.*)/$', views.BookModelViewSet.as_view({'get': 'retrieve', 'post':'create', 'put': 'update', 'patch': 'partial_update', 'delete': 'destroy'})),
]

接口测试

群查

单查

单删

查看数据库

单增

入库成功

等等

总结

GenericAPIView 与 APIView 的区别与适用场景

1. GenericAPIView 视图类

GenericView 继承 GenericAPIView 视图类

适用于标准的接口请求，或实现标准的 Model 类操作接口。

案例： 用户查询时，发送 GET 请求，返回数据。

2. APIView 视图类

ViewSet 继承 APIView 视图类

实现不需要 Model 类操作，或非标准的 Model 类操作接口。比如，POST请求在标准的 Model 类操作用于新增接口，但以下案例并不符合这个标准。

案例 1： 请求手机验证码时，发送 POST 请求，不需要 Model 类的参与。

案例 2： 用户登录时，发送的 POST 请求，并不是完成数据的新增。POST 只是用于提交数据，返回值也不是登录用户信息，而是登录的认证信息。