在Django学习[60]中的views.py的类视图中，使用继承了viewsets.ModelViewSet

Viewsets

ViewSetMixin

class ViewSetMixin:
    """
    This is the magic.

    Overrides `.as_view()` so that it takes an `actions` keyword that performs
    the binding of HTTP methods to actions on the Resource.

    For example, to create a concrete view binding the 'GET' and 'POST' methods
    to the 'list' and 'create' actions...

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

    @classonlymethod
    def as_view(cls, actions=None, **initkwargs):
        """
        Because of the way class based views create a closure around the
        instantiated view, we need to totally reimplement `.as_view`,
        and slightly modify the view function that is created and returned.
        """
        # The name and description initkwargs may be explicitly overridden for
        # certain route configurations. eg, names of extra actions.
        cls.name = None
        cls.description = None

        # The suffix initkwarg is reserved for displaying the viewset type.
        # This initkwarg should have no effect if the name is provided.
        # eg. 'List' or 'Instance'.
        cls.suffix = None

        # The detail initkwarg is reserved for introspecting the viewset type.
        cls.detail = None

        # Setting a basename allows a view to reverse its action urls. This
        # value is provided by the router through the initkwargs.
        cls.basename = None

        # actions must not be empty
        if not actions:
            raise TypeError("The `actions` argument must be provided when "
                            "calling `.as_view()` on a ViewSet. For example "
                            "`.as_view({'get': 'list'})`")

        # sanitize keyword arguments
        for key in initkwargs:
            if key in cls.http_method_names:
                raise TypeError("You tried to pass in the %s method name as a "
                                "keyword argument to %s(). Don't do that."
                                % (key, cls.__name__))
            if not hasattr(cls, key):
                raise TypeError("%s() received an invalid keyword %r" % (
                    cls.__name__, key))

        # name and suffix are mutually exclusive
        if 'name' in initkwargs and 'suffix' in initkwargs:
            raise TypeError("%s() received both `name` and `suffix`, which are "
                            "mutually exclusive arguments." % (cls.__name__))

        def view(request, *args, **kwargs):
            self = cls(**initkwargs)

            if 'get' in actions and 'head' not in actions:
                actions['head'] = actions['get']

            # We also store the mapping of request methods to actions,
            # so that we can later set the action attribute.
            # eg. `self.action = 'list'` on an incoming GET request.
            self.action_map = actions

            # Bind methods to actions
            # This is the bit that's different to a standard view
            for method, action in actions.items():
                handler = getattr(self, action)
                setattr(self, method, handler)

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

            # And continue as usual
            return self.dispatch(request, *args, **kwargs)

        # take name and docstring from class
        update_wrapper(view, cls, updated=())

        # and possible attributes set by decorators
        # like csrf_exempt from dispatch
        update_wrapper(view, cls.dispatch, assigned=())

        # We need to set these on the view function, so that breadcrumb
        # generation can pick out these bits of information from a
        # resolved URL.
        view.cls = cls
        view.initkwargs = initkwargs
        view.actions = actions
        return csrf_exempt(view)

第15行重写了as_view，添加了一些过滤和反向解析

GenericViewSet

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

继承自generics.GenericAPIView 和 ViewSetMixin

generics.GenericAPIView在上一篇已经介绍过。

ViewSet

class ViewSet(ViewSetMixin, views.APIView):
    """
    The base ViewSet class does not provide any actions by default.
    """
    pass

默认什么都不支持，需要自己手动实现

ReadOnlyModelViewSet

只读的模型的视图集合

class ReadOnlyModelViewSet(mixins.RetrieveModelMixin,
                           mixins.ListModelMixin,
                           GenericViewSet):
    """
    A viewset that provides default `list()` and `retrieve()` actions.
    """
    pass

• 继承自：

  • mixins.RetrieveModelMixin
  • mixins.ListModelMixin
  • GenericViewSet
• 只能获取数据，所以只读

ModelViewSet

直接封装对象的所有操作

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

• 继承自：

  • mixins.CreateModelMixin
  • mixins.RetrieveModelMixin
  • mixins.UpdateModelMixin
  • mixins.DestroyModelMixin
  • mixins.ListModelMixin
  • GenericViewSet

总结这些viewset作用就是，将CRUD这些进行组合，并且重写了as_view以便于和路由对接。

Viewset实践

上一篇直接继承了ListCreateAPIView，现在使用封装后的Viewsets作为继承的视图类。

Views.py

新建一个class类

class GameModelViewSet(ModelViewSet):

    serializer_class = GameSerializer

    queryset = Game.objects.all()

urls.py

注册路由时，也可以使用as_view,但是比较麻烦，所以使用router来代替

router = DefaultRouter()

router.register(r'games', GameModelViewSet)

总URLS

from django.contrib import admin
from django.urls import path, include

from App.urls import router

urlpatterns = [
    path('admin/', admin.site.urls),
    # path('app/', include('App.urls')),
    path('app/', include(router.urls)),
]

postman测试

get访问所有数据

post新建

get访问单个数据

delete步骤自行测试

restframework分页器

开发文档:https://q1mi.github.io/Django-REST-framework-documentation/api-guide/pagination_zh/

当开发完接口之后，需要实现接口数据的分片，比如每次只返回5条数据给客户端，而不是每次都返回全部数量这样能有效减少服务器压力，减少客户端的加载时间，提高响应速度，客户端需要携带参数访问接口。

分页器类型介绍

分页器分为三种:

• PageNumberPagination

  • 常规单页分页器
  • 通过page参数访问某一个单个分片数据

• LimitOffsetPagination

  • 偏移分页
  • 这种分页样式反映了查找多个数据库记录时使用的语法。客户端包括“limit”和“offset”查询参数。limit指示要返回的项目的最大数目，这相当于其他样式中的 page_size。offset指示查询相对于完整的未分页项的起始位置。

• CursorPagination

  • 游标分页
  • 基于cursor的分页提供了一个不透明的“游标”指示器，客户端可以使用它对结果集进行分页。这种分页样式只显示正向和反向控件，而不允许客户端导航到任意位置。

基于cursor的分页要求结果集中的项具有唯一的、不变的顺序。此顺序通常可能是记录上的创建时间戳，因为它提为分页供了一致的顺序。
基于cursor的分页比其他方案更复杂。它还要求结果集呈现固定的顺序，并且不允许客户端任意索引结果集。但是，它确实提供了以下好处：

  - 提供一致的分页视图。当恰当地使用时，`CursorPagination` 可以确保客户端在翻阅记录时永远不会看到同一个项目两次，即使在分页过程中其他客户端正在插入新的项目时亦是如此。
  - 支持使用非常大的数据集。对于极其庞大的数据集，使用基于offset的分页样式进行分页可能会变得效率低下或无法使用。基于cursor的分页方案具有固定时间的属性，并且不会随着数据集大小的增加而减慢。

实践

首先在views中注册分页器:

class LargeResultsSetPagination(PageNumberPagination):
    page_size = 2
    page_size_query_param = 'page_size'
    max_page_size = 8

在Viewset类视图中使用分页器:

class GameModelViewSet(ModelViewSet):
    serializer_class = GameSerializer

    queryset = Game.objects.all()

    pagination_class = LargeResultsSetPagination

接着进行携带page参数get请求接口:


可以看到只返回了两条数据，并且客户端通过循环page参数，可继续读取下面的数据。

总结

router

使用了ViewSet，封装了路由的设置，可以直接使用router来自动设置路由路径

功能

想要实现对应的功能，只需要继承对应minxins中的类即可：

• mixins.CreateModelMixin
• mixins.RetrieveModelMixin
• mixins.UpdateModelMixin
• mixins.DestroyModelMixin
• mixins.ListModelMixin

• GenericViewSet
  

  APIView

• 子类

  • generics包中

  • GenericAPIView

    • 增加的模型的获取操作
    • get_queryset

    • get_object

      • lookup_field 默认pk
    • get_serializer
    • get_serializer_class
    • get_serializer_context
    • filter_queryset
    • paginator
    • paginate_queryset
    • get_paginated_response

  • CreateAPIView

    • 创建的类视图
    • 继承自GenericAPIView
    • 继承自CreateModelMixin
    • 实现了post进行创建

  • ListAPIView

    • 列表的类视图
    • 继承自GenericAPIView
    • 继承自ListModelMixin
    • 实现了get

  • RetrieveAPIView

    • 查询单个数据的类视图
    • 继承自GenericAPIView
    • 继承自RetrieveModelMixin
    • 实现了get

  • DestroyAPIView

    • 销毁数据的类视图，删除数据的类视图
    • 继承自GenericAPIView
    • 继承自DestroyModelMixin
    • 实现了delete

  • UpdateAPIView

    • 更新数据的类视图
    • 继承自GenericAPIView
    • 继承自UpdateModelMixin
    • 实现了 put,patch

  • ListCreateAPIView

    • 获取列表数据，创建数据的类视图
    • 继承自GenericAPIView
    • 继承自ListModelMixin
    • 继承自CreateModelMixin
    • 实现了 get,post

  • RetrieveUpdateAPIView

    • 获取单个数据，更新单个数据的类视图
    • 继承自GenericAPIView
    • 继承自RetrieveModelMixin
    • 继承自UpdateModelMixin
    • 实现了 get, put, patch

  • RetrieveDestroyAPIView

    • 获取单个数据，删除单个数据
    • 继承自GenericAPIView
    • 继承自RetrieveModelMixin
    • 继承自DestroyModelMixin
    • 实现了 get, delete

  • RetrieveUpdateDestroyAPIView

    • 获取单个数据，更新单个数据，删除单个数据的类视图
    • 继承自GenericAPIView
    • 继承自RetrieveModelMixin
    • 继承自UpdateModelMixin
    • 继承自DestroyModelMixin
    • 实现了 get, put, patch, delete

• mixins

  • CreateModelMixin

    • create
    • perform_create
    • get_success_headers

  • ListModelMixin

    • list

      • 查询结果集，添加分页，帮你序列化

  • RetrieveModelMixin

    • retrieve

      • 获取单个对象并进行序列化

  • DestroyModelMixin

    • destroy

      • 获取单个对象
      • 调用执行删除
      • 返回Respon 状态码204

    • perform_destroy

      • 默认是模型的delete

      • 如果说数据的逻辑删除

        • 重写进行保存

  • UpdateModelMixin

    • update

      • 获取对象，合法验证
      • 执行更新
    • perform_update

    • partial_update

      • 差量更新，对应的就是patch

• viewsets

  • ViewSetMixin

    • 重写as_view

  • GenericViewSet

    • 继承自GenericAPIView
    • 继承自ViewSetMixin

  • ViewSet

    • 继承自APIView
    • 继承自ViewSetMixin
    • 默认啥都不支持，需要自己手动实现

  • ReadOnlyModelViewSet

    • 只读的模型的视图集合
    • 继承自RetrieveModelMixin
    • 继承自ListModelMixin
    • 继承自GenericViewSet

  • ModelViewSet

    • 直接封装对象的所有操作
    • 继承自GenericViewSet
    • 继承自CreateModelMixin
    • 继承自RetrieveModelMixin
    • 继承自UpdateModelMixin
    • 继承自DestroyModelMixin
    • 继承自ListModelMixin