drf群查接口之分页器与过滤器

分页器的使用详解

rest_framework.mixins.py

# 分页器一般用于群查接口
class ListModelMixin:
    """
    List a queryset.
    """
    def list(self, request, *args, **kwargs):
        queryset = self.filter_queryset(self.get_queryset())
		
        # 先过滤，后分页
        # self.paginate_queryset由继承GenericAPIView而来
        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)

GenericAPIView类

pagination_class = api_settings.DEFAULT_PAGINATION_CLASS

@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
    # 调用View视图类中配置的paginator的paginate_queryset方法
    # paginatior是一个方法属性来反射获取pagination_class
    return self.paginator.paginate_queryset(queryset, self.request, view=self)

drf自带的几种分页器

from rest_framework.pagination import PageNumberPagination as DrfPageNumberPagination

class PageNumberPagination(DrfPageNumberPagination):
    # 默认一页显示的条数
    page_size = 2
    # url中携带页码的key
    page_query_param = 'page'
    # url中用户携带自定义一页条数的key
    page_size_query_param = 'page_size'
    # 用户最大可自定义一页的条数
    max_page_size = 3


from rest_framework.pagination import LimitOffsetPagination as DrfLimitOffsetPagination
class LimitOffsetPagination(DrfLimitOffsetPagination):
    # 默认一页显示的条数
    default_limit = 2
    # url中用户携带自定义一页条数的key
    limit_query_param = 'limit'
    # url中用户携带自定义偏移条数的key
    offset_query_param = 'offset'
    # 用户最大可自定义一页的条数
    max_limit = 2


from rest_framework.pagination import CursorPagination as DrfCursorPagination
class CursorPagination(DrfCursorPagination):
    # 默认一页显示的条数
    page_size = 2
    # url中携带页码的key（编码后的结果）
    cursor_query_param = 'cursor'
    # url中用户携带自定义一页条数的key
    page_size_query_param = 'page_size'
    # 用户最大可自定义一页的条数
    max_page_size = 3
    # 游标分页器的特殊点：
    # 1）如果视图类没有配 排序过滤组件filter_backends = [OrderingFilter]，采用 ordering 设置的作为默认排序规则
    # 2）如果视图类配了 排序过滤组件filter_backends = [OrderingFilter]，url请求必须带上ordering排序规则，因为默认排序规则失效
    # 注：因为游标分页是基于排序后结果上的分页
    ordering = '-price'

过滤器

过滤器中有自带的排序组件

"""ORDERING_PARAM
排序组件
1）在视图文件views.py中导入drf的搜索组件
from rest_framework.filters import OrderingFilter

2）将搜索组件配置给群查接口视图类的filter_backends
filter_backends = [OrderingFilter]

3）配置视图类关联的Model表允许排序的字段
ordering_fields = ['id', 'price']

4）前台访问该群查接口，采用拼接参数方式用search关键字将搜索目标提供给后台
http://127.0.0.1:8000/course/free/?ordering=price,-id  # 按price升序，如果price相同，再按id降序
"""

自定义过滤组件

"""
自定义过滤器
1）自定义类实现filter_queryset方法即可，接收request, queryset, view参数

2）制定过滤条件，将过滤成功后的queryset返回即可，如果过滤失败，返回原样的queryset

3）将自定义过滤类配置给群查视图类的filter_backends
"""

filter.py

# 前台接口：/course/free/?count=2 ，代表只对前台返回2条数据
class CountFilter:
    def filter_queryset(self, request, queryset, view):
        count = request.query_params.get('count', None)
        try:
            # TODO: 切片后的queryset不能再做ORM Q查询，如何实现queryset切片，现在再过滤时后配置
            # 结论：drf的搜索组件和排序组件都是建立在表的所有数据基础上的过滤规则，所以该自定义过滤类在视图类配置中
            # filter_backends = [SearchFilter, OrderingFilter, CountFilter] 必须在前两者之后
            return queryset[:int(count)]
        except:
            return queryset

搜索过滤

'''
# 分页组件：基础分页(采用)、偏移分页、游标分页(了解)
from rest_framework.pagination import PageNumberPagination, LimitOffsetPagination, CursorPagination
from . import pagination

# 过滤组件：搜索功能、排序功能
from rest_framework.filters import SearchFilter, OrderingFilter
from .filters import CountFilter
class CourseViewSet(GenericViewSet, ListModelMixin):
    queryset = models.Course.objects.filter(is_delete=False, is_show=True).all()
    serializer_class = serializers.CourseSerializer

    # 分页组件
    # 方法一：直接使用drf分页类，在视图类中完成分页类的必要配置
    # pagination_class = PageNumberPagination
    # PageNumberPagination.page_size = 1

    # 方法二：自定义分页类继承drf分页类，在自定义分页类中完成配置，视图类中使用自定义分页类
    # 基础分页器
    # pagination_class = pagination.PageNumberPagination
    # 偏移分页器，没有固定页码，自定义从偏移量开始往后查询自定义条数
    # pagination_class = pagination.LimitOffsetPagination
    # 游标分页器
    # pagination_class = pagination.CursorPagination

    # 过滤组件：实际开发，有多个过滤条件时，要把优先级高的放在前面
    filter_backends = [SearchFilter, OrderingFilter, CountFilter]
    # 参与搜索的字段
    search_fields = ['name', 'id']

    # 允许排序的字段
    ordering_fields = ['id', 'price']

'''

high_mark和low_mark控制切queryset的大小

queryset.query.high_mark = None
queryset.query.low_mark = 0

# 实际是对queryset的克隆，修改low_mark=1,high_mark=10
new_queryset = queryset[1,10]

分类过滤和区间过滤

fitler.py

class CourseFilterSet(filterset.FilterSet):
    max_price = filters.NumberFilter(field_name='price', lookup_expr='lte')
    min_price = filters.NumberFilter(field_name='price', lookup_expr='gte')
    class Meta:
        model = models.Course
        fields = ['max_price', 'min_price','course_category']

views.py

class CourseViewSet(viewsets.GenericViewSet, mixins.ListModelMixin):
    queryset = models.Course.objects.filter(is_delete=False, is_show=True)
    serializer_class = serializers.CourseModelSerializer
    # 过滤
    filter_backends = [DjangoFilterBackend]
    # max_price=100&min_price=20&course_category=1 
    # 为django-filter配置，区间分页
    filterset_class = CourseFilterSet

    
# 阅读django-filter的源码可以发现直接在view视图里声明filterset_fields=['course_category']也可以完成分类过滤