Django rest framework（8）---- 视图和渲染器

django rest framework 之视图

序列化器    PagerSerialiser

from rest_framework import serializers
from api import models

class PagerSerialiser(serializers.ModelSerializer):
    class Meta:
        model = models.Role
        fields = "__all__"

APIview

ApiAPIView 实现分页的写法如下

from api.utils.serializsers.pager import PagerSerialiser
from rest_framework.response import Response
from rest_framework.pagination import PageNumberPagination,LimitOffsetPagination,CursorPagination
from api import models

class MyCursorPagination(CursorPagination):
    cursor_query_param = 'cursor'
    page_size = 2
    ordering = 'id'
    page_size_query_param = None
    max_page_size = None

class Pager1View(APIView):

    def get(self,request,*args,**kwargs):

        # 获取所有数据
        roles = models.Role.objects.all()

        # 创建分页对象
        # pg = CursorPagination()
        pg = MyCursorPagination()

        # 在数据库中获取分页的数据
        pager_roles = pg.paginate_queryset(queryset=roles,request=request,view=self)

        # 对数据进行序列化
        ser = PagerSerialiser(instance=pager_roles, many=True)

        # return Response(ser.data)
        return pg.get_paginated_response(ser.data)

添加路由

urlpatterns = [
    url(r'^(?P<version>[v1|v2]+)/pager1/$', views.Pager1View.as_view()),
]

测试结果

http://127.0.0.1:8000/api/v1/pager1/

GenericAPIView 我们一般不用，没有比APIView 简单多少

GenericAPIView 是继承APIView的，所以对APIView 进行了一些功能的封装，同样实现上述功能，代码如下

from api.utils.serializsers.pager import PagerSerialiser
from rest_framework.generics import GenericAPIView

class View1View(GenericAPIView):
    queryset = models.Role.objects.all() # 指定查询的数据
    serializer_class = PagerSerialiser    # 序列化
    pagination_class = PageNumberPagination  # 分页
    def get(self,request,*args,**kwargs):
        # 获取数据
        roles = self.get_queryset() # models.Role.objects.all()

        # [1, 1000,]     [1,10]
        pager_roles = self.paginate_queryset(roles) # 获取分页后的结果

        # 序列化
        ser = self.get_serializer(instance=pager_roles,many=True)

        return Response(ser.data)

源码如下所示

class GenericAPIView(views.APIView):
    """
    Base class for all other generic views.
    """
    # You'll need to either set these attributes,
    # or override `get_queryset()`/`get_serializer_class()`.
    # If you are overriding a view method, it is important that you call
    # `get_queryset()` instead of accessing the `queryset` property directly,
    # as `queryset` will get evaluated only once, and those results are cached
    # for all subsequent requests.
    queryset = None
    serializer_class = None

    # If you want to use object lookups other than pk, set 'lookup_field'.
    # For more complex lookup requirements override `get_object()`.
    lookup_field = 'pk'
    lookup_url_kwarg = None

    # The filter backend classes to use for queryset filtering
    filter_backends = api_settings.DEFAULT_FILTER_BACKENDS

    # The style to use for queryset pagination.
    pagination_class = api_settings.DEFAULT_PAGINATION_CLASS

    def get_queryset(self):
        """
        Get the list of items for this view.
        This must be an iterable, and may be a queryset.
        Defaults to using `self.queryset`.

        This method should always be used rather than accessing `self.queryset`
        directly, as `self.queryset` gets evaluated only once, and those results
        are cached for all subsequent requests.

        You may want to override this if you need to provide different
        querysets depending on the incoming request.

        (Eg. return a list of items that is specific to the user)
        """
        assert self.queryset is not None, (
            "'%s' should either include a `queryset` attribute, "
            "or override the `get_queryset()` method."
            % self.__class__.__name__
        )

        queryset = self.queryset
        if isinstance(queryset, QuerySet):
            # Ensure queryset is re-evaluated on each request.
            queryset = queryset.all()
        return queryset

    def get_object(self):
        """
        Returns the object the view is displaying.

        You may want to override this if you need to provide non-standard
        queryset lookups.  Eg if objects are referenced using multiple
        keyword arguments in the url conf.
        """
        queryset = self.filter_queryset(self.get_queryset())

        # Perform the lookup filtering.
        lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field

        assert lookup_url_kwarg in self.kwargs, (
            'Expected view %s to be called with a URL keyword argument '
            'named "%s". Fix your URL conf, or set the `.lookup_field` '
            'attribute on the view correctly.' %
            (self.__class__.__name__, lookup_url_kwarg)
        )

        filter_kwargs = {self.lookup_field: self.kwargs[lookup_url_kwarg]}
        obj = get_object_or_404(queryset, **filter_kwargs)

        # May raise a permission denied
        self.check_object_permissions(self.request, obj)

        return obj

    def get_serializer(self, *args, **kwargs):
        """
        Return the serializer instance that should be used for validating and
        deserializing input, and for serializing output.
        """
        serializer_class = self.get_serializer_class()
        kwargs['context'] = self.get_serializer_context()
        return serializer_class(*args, **kwargs)

    def get_serializer_class(self):
        """
        Return the class to use for the serializer.
        Defaults to using `self.serializer_class`.

        You may want to override this if you need to provide different
        serializations depending on the incoming request.

        (Eg. admins get full serialization, others get basic serialization)
        """
        assert self.serializer_class is not None, (
            "'%s' should either include a `serializer_class` attribute, "
            "or override the `get_serializer_class()` method."
            % self.__class__.__name__
        )

        return self.serializer_class

    def get_serializer_context(self):
        """
        Extra context provided to the serializer class.
        """
        return {
            'request': self.request,
            'format': self.format_kwarg,
            'view': self
        }

    def filter_queryset(self, queryset):
        """
        Given a queryset, filter it with whichever filter backend is in use.

        You are unlikely to want to override this method, although you may need
        to call it either from a list view, or from a custom `get_object`
        method if you want to apply the configured filtering backend to the
        default queryset.
        """
        for backend in list(self.filter_backends):
            queryset = backend().filter_queryset(self.request, queryset, self)
        return queryset

    @property
    def paginator(self):
        """
        The paginator instance associated with the view, or `None`.
        """
        if not hasattr(self, '_paginator'):
            if self.pagination_class is None:
                self._paginator = None
            else:
                self._paginator = self.pagination_class()
        return self._paginator

    def paginate_queryset(self, queryset):
        """
        Return a single page of results, or `None` if pagination is disabled.
        """
        if self.paginator is None:
            return None
        return self.paginator.paginate_queryset(queryset, self.request, view=self)

    def get_paginated_response(self, data):
        """
        Return a paginated style `Response` object for the given output data.
        """
        assert self.paginator is not None
        return self.paginator.get_paginated_response(data)

添加路由

urlpatterns = [
    url(r'^(?P<version>[v1|v2]+)/pager1/$', views.Pager1View.as_view()),
    # url(r'^(?P<version>[v1|v2]+)/v1/$', views.View1View.as_view()),

]

　　

测试结果如下

http://127.0.0.1:8000/api/v1/v1/

GenericViewSet

它继承的是

它在 GenericAPIView 的基础上增加了路由和视图函数的限制关系，在url中指定的方法类视图中必须对应

from api.utils.serializsers.pager import PagerSerialiser
from rest_framework.viewsets import GenericViewSet

class View1View(GenericViewSet):
    queryset = models.Role.objects.all()
    serializer_class = PagerSerialiser
    pagination_class = PageNumberPagination

    def list(self, request, *args, **kwargs):
        # 获取数据
        roles = self.get_queryset()  # models.Role.objects.all()

        # [1, 1000,]     [1,10]
        pager_roles = self.paginate_queryset(roles)

        # 序列化
        ser = self.get_serializer(instance=pager_roles, many=True)

        return Response(ser.data)

添加路由

urlpatterns = [
    url(r'^(?P<version>[v1|v2]+)/pager1/$', views.Pager1View.as_view()),
    # url(r'^(?P<version>[v1|v2]+)/v1/$', views.View1View.as_view()),
    url(r'^(?P<version>[v1|v2]+)/v1/$', views.View1View.as_view({'get': 'list'})),

]

测试结果如下

ModelViewSet

它继承的类如下，它实现的功能比较强大，只需简单的配置，就不需要我们去写增删改查和局部更新，在这里可以解决我们这样的一个问题，当我们查询所有数据的时候直接会去用list方法，查询一个通过url/1 会执行 retrieve 方法 ，省去我们的判断

继承的其中一个类的源代码如下，我们可以看到只要继承了这个方法，我们就不需要写list 查询全部数据的方法

class ListModelMixin(object):
    """
    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)

通过继承modelViewSet实现分页的功能如下

from api.utils.serializsers.pager import PagerSerialiser
from rest_framework.viewsets import GenericViewSet,ModelViewSet

class View1View(ModelViewSet):
    queryset = models.Role.objects.all()
    serializer_class = PagerSerialiser
    pagination_class = PageNumberPagination

配置路由

urlpatterns = [
    url(r'^(?P<version>[v1|v2]+)/pager1/$', views.Pager1View.as_view()),
    # url(r'^(?P<version>[v1|v2]+)/v1/$', views.View1View.as_view()),
    # url(r'^(?P<version>[v1|v2]+)/v1/$', views.View1View.as_view({'get': 'list'})),
    url(r'^(?P<version>[v1|v2]+)/v1/(?P<pk>\d+)/$', views.View1View.as_view({'get': 'retrieve','delete':'destroy','put':'update','patch':'partial_update'})),

]

测试结果如下

http://127.0.0.1:8000/api/v1/v1/1/

　　

在上面我们可以看到，我们可以对这一条数据，进行增删改查的操作

django rest framework 之渲染器

通过渲染器可以指定数据返回的格式

注册 rest_framework

全局配置

REST_FRAMEWORK = {

    "DEFAULT_RENDERER_CLASSES":[
        'rest_framework.renderers.JSONRenderer',
        'rest_framework.renderers.BrowsableAPIRenderer',
    ]
}

局部配置

class TestView(APIView):
    # renderer_classes = [JSONRenderer,BrowsableAPIRenderer]
    def get(self, request, *args, **kwargs):
        # 获取所有数据
        roles = models.Role.objects.all()

        # 创建分页对象
        # pg = CursorPagination()
        pg = MyCursorPagination()

        # 在数据库中获取分页的数据
        pager_roles = pg.paginate_queryset(queryset=roles, request=request, view=self)

        # 对数据进行序列化
        ser = PagerSerialiser(instance=pager_roles, many=True)

        return Response(ser.data)