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
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