标签：attr result 传参数 war provides 逻辑 col min attrs
前言：
分页大家应该都很清楚，今天我来给大家做一下Django的rest_framework的分页组件的分析；我的讲解的思路是这样的，分别使用APIview的视图类和基于ModelViewSet的视图类两种方式实现分页的功能，同时我也会介绍两个分页的类，PageNumberPagination类和LimitOffsetPagination，希望能对大家有所帮助！
今天的博客主要的这样的，先讲解基于APIView类的两种分页类的实现方式，然后在讲解基于ModelViewSet类的两种分页类的实现方式
正文：
1、先导入我们要用到的分页的类
from rest_framework.pagination import PageNumberPagination
2、下面我们来看下这个这个类的类是属性
class PageNumberPagination(BasePagination):
"""
A simple page number based style that supports page numbers as
query parameters. For example:
http://api.example.org/accounts/?page=4
http://api.example.org/accounts/?page=4&page_size=100
"""
# The default page size.
# Defaults to `None`, meaning pagination is disabled.
page_size = api_settings.PAGE_SIZE
django_paginator_class = DjangoPaginator
# Client can control the page using this query parameter.
page_query_param = ‘page‘
page_query_description = _(‘A page number within the paginated result set.‘)
# Client can control the page size using this query parameter.
# Default is ‘None‘. Set to eg ‘page_size‘ to enable usage.
page_size_query_param = None
page_size_query_description = _(‘Number of results to return per page.‘)
# Set to an integer to limit the maximum page size the client may request.
# Only relevant if ‘page_size_query_param‘ has also been set.
max_page_size = None
last_page_strings = (‘last‘,)
template = ‘rest_framework/pagination/numbers.html‘
invalid_page_message = _(‘Invalid page.‘)
这里我们重点介绍一下类的属性，重点的参数如下，等下我们会测试的
3、然后看下类的paginate_queryset方法，这个方法主要就是用来显示数据的
def paginate_queryset(self, queryset, request, view=None):
"""
Paginate a queryset if required, either returning a
page object, or `None` if pagination is not configured for this view.
"""
page_size = self.get_page_size(request)
if not page_size:
return None
paginator = self.django_paginator_class(queryset, page_size)
page_number = request.query_params.get(self.page_query_param, 1)
if page_number in self.last_page_strings:
page_number = paginator.num_pages
try:
self.page = paginator.page(page_number)
except InvalidPage as exc:
msg = self.invalid_page_message.format(
page_number=page_number, message=six.text_type(exc)
)
raise NotFound(msg)
if paginator.num_pages > 1 and self.template is not None:
# The browsable API should display pagination controls.
self.display_page_controls = True
self.request = request
return list(self.page)
4、PageNumberPagination用到知识点，我们已经讲解完了，下面我们介绍下如何使用，首先我们先继承一下PageNumberPagination，然后自定义我们的参数
class MyPageNumberPagination(PageNumberPagination):
page_size = 1
page_query_param = "mypage"
page_size_query_param = "size"
max_page_size = 4
last_page_strings = (‘mylast‘,)
5、然后在视图类中使用我们自己写的分页类
class Book_cbv(APIView):
authentication_classes = []
# permission_classes = [SVIPpermission(),]
# throttle_classes = [throttlerate(),]
# parser_classes = []
def get(self,request):
query_list = models.Book.objects.all()
mypageobj = MyPageNumberPagination()
obj = mypageobj.paginate_queryset(queryset=query_list,request=request,view=None)
bs = bookmodelserializer(obj,many=True,context={‘request‘: request})
重点看下这里，关注一下paginate_queryset这个方法的参数，和源码中的参数对应一下
源码中的参数
6、下面我们测试一下
每页显示一条数据，显示第一页
每页显示1条数据，显示第二页
类中设定每页显示1条数据，我们临时修改为显示2条数据，显示第一页
类中设定每页显示1条数据，我们临时修改为显示5条数据，显示第一页,理论上5是不生效的，实际只显示了4条数据
经过测试，我们上面的四个参数都已经生效
最后在补充一点，上面的每页显示多少条的设置针对单个表生效，如何基于所有的表生效。
class PageNumberPagination(BasePagination):
"""
A simple page number based style that supports page numbers as
query parameters. For example:
http://api.example.org/accounts/?page=4
http://api.example.org/accounts/?page=4&page_size=100
"""
# The default page size.
# Defaults to `None`, meaning pagination is disabled.
page_size = api_settings.PAGE_SIZE
然后看下api_setttings水里对象
api_settings = APISettings(None, DEFAULTS, IMPORT_STRINGS)
看下APISettigns这个类
def __init__(self, user_settings=None, defaults=None, import_strings=None):
if user_settings:
self._user_settings = self.__check_user_settings(user_settings)
self.defaults = defaults or DEFAULTS
self.import_strings = import_strings or IMPORT_STRINGS
self._cached_attrs = set()
到了这里，我们大致就知道了，我们需要进入我们的project的settings文件中进行设置
REST_FRAMEWORK = {
# "DEFAULT_AUTHENTICATION_CLASSES":(
# "app1.utils.Book_auther",
# ),
# "DEFAULT_PERMISSION_CLASSES_CLASSES": (
# "app1.utils.SVIPpermission",
# ),
# "DEFAULT_DEFAULT_THROTTLE_CLASSES_CLASSES": (
# "app1.utils.throttlerate",
# )
"PAGE_SIZE" : 2,
}
1、导入LimitOffsetPagination类
from rest_framework.pagination import LimitOffsetPagination
2、我们同样看下这个类的属性
class LimitOffsetPagination(BasePagination):
"""
A limit/offset based style. For example:
http://api.example.org/accounts/?limit=100
http://api.example.org/accounts/?offset=400&limit=100
"""
default_limit = api_settings.PAGE_SIZE
limit_query_param = ‘limit‘
limit_query_description = _(‘Number of results to return per page.‘)
offset_query_param = ‘offset‘
offset_query_description = _(‘The initial index from which to return the results.‘)
max_limit = None
template = ‘rest_framework/pagination/numbers.html‘
重点看下下面几个属性
3、然后看下LimitOffsetPagination类的paginate_queryset的方法
def paginate_queryset(self, queryset, request, view=None):
self.count = self.get_count(queryset)
self.limit = self.get_limit(request)
if self.limit is None:
return None
self.offset = self.get_offset(request)
self.request = request
if self.count > self.limit and self.template is not None:
self.display_page_controls = True
if self.count == 0 or self.offset > self.count:
return []
return list(queryset[self.offset:self.offset + self.limit])
4、然后我们看下如何在我们的视图类中使用这个分页插件，其实和前面的插件的用法是一样的，只是参数不一样而已
class Book_cbv(APIView):
authentication_classes = []
# permission_classes = [SVIPpermission(),]
# throttle_classes = [throttlerate(),]
# parser_classes = []
def get(self,request):
query_list = models.Book.objects.all()
# mypageobj = MyPageNumberPagination()
# obj = mypageobj.paginate_queryset(queryset=query_list,request=request,view=None)
mypageobj = MyLimitOffsetPagination()
obj = mypageobj.paginate_queryset(queryset=query_list,request=request,view=None)
bs = bookmodelserializer(obj,many=True,context={‘request‘: request})
return Response(bs.data)
重点是这里
5、最后我们测试一下
默认不传参数，每页显示2条
临时修改每页显示为1个，偏移量为1
临时修改每页显示1条，偏移量为2
通过上面的讲解，我们知道两个分页的类就是参数不一样，使用的逻辑都一样，我们这里就不分开讲解2个类，只讲一下如何ModelViewSet类实现分页
1、先看下基于ModelViewSet的视图类
from rest_framework import viewsets
class AutherModelCBV(viewsets.ModelViewSet):
queryset = models.Auther.objects.all()
serializer_class = authermodelserializer
2、因为这个ModelViewSet这个类重写了list方法，分页肯定在list方法中，所以我们先要找到list方法，ModelViewSet这个类一共有4个父类
3、我们看下mixins.ListModelMixin这个类，因为list方法是在这个类中实现的，进入这个类，看下list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)
4、重点看下paginate_queryset这个方法，首先要先找到这个方法
5、如果找这个方法呢，我们从最开始找这个方法
首先AutherModelCBV这个类没有这个方法
from rest_framework import viewsets
class AutherModelCBV(viewsets.ModelViewSet):
queryset = models.Auther.objects.all()
serializer_class = authermodelserializer
然后去ModelViewSet类中找这个方法，同样没有
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
ModelViewSet这个类继承了有5个类，我们从左到右一个一个看，最终在GenericViewSet，我们看到这个类还继承了2个类
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
再次从左到右依次查找paginate_queryset这个方法，最终下面这个类中找到这个方法
class GenericAPIView(views.APIView):
方法的源码如下
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)
那么这个paginator是什么呢，原来他是静态方法
@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
到这里，我们就非常清楚的了，我们需要在我们自己的视图类中定义一个这样的属性，然后把我们的分页类赋值给pagination_class这个属性就可以了
6、然后看下在ModelViewSet类中如何操作
from rest_framework import viewsets
class AutherModelCBV(viewsets.ModelViewSet):
queryset = models.Auther.objects.all()
serializer_class = authermodelserializer
pagination_class = MyPageNumberPagination
重点看下这里
最后我们测试一下
下面这个是我们禁用分页的显示效果
下面开始启用分页的效果,显示第一页
显示第二页的效果
总结：至此，Django的Rest_framework的分页组件就介绍完了，大家有不清楚的，可以留言，我们共同进步。
Django的rest_framework的分页组件源码分析
标签：attr result 传参数 war provides 逻辑 col min attrs
原文地址：https://www.cnblogs.com/bainianminguo/p/10508191.html
