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在django rest框架中重写cursorpagination的页面大小和顺序

django-rest-framework django

KitKit · 技术社区 · 6 年前

我使用django rest框架的cursorpagination,我想覆盖默认值 page_size(10) 和 ordering('timestamp') 在单个视图集中。我该怎么做呢?

我试过使用我的视图集,但没有成功:

from rest_framework.pagination import CursorPagination
class ListAPIView(ListAPIView):
    queryset = Cake.objects.all()
    permission_classes = [AllowAny]
    serializer_class = ListSerializer
    pagination_class = CursorPagination
    filter_backends = (OrderingFilter, DjangoFilterBackend)
    filter_class = CakeListFilter
    filterset_fields = ('cake_type', 'user__username')
    ordering = '-date'
    page_size = 5

1 回复 | 直到 6 年前

ivissani 6 年前

您可以创建一个继承自 CursorPagination 类以设置自定义 page_size 和/或 max_page_size 像这样:

class CustomPageSizeCursorPagination(CursorPagination):
    page_size = 5
    max_page_size = 100

然后用这个类作为 pagination_class 视图集的字段

警告:以下代码未经测试

另一个选项是编写一个自定义分页器类,该类从视图集中获取页面大小。例如:

class PageSizeInViewSetCursorPagination(CursorPagination):
    def get_page_size(self, request, viewset_page_size):
        if self.page_size_query_param:
            try:
                return _positive_int(
                    request.query_params[self.page_size_query_param],
                    strict=True,
                    cutoff=self.max_page_size
                )
            except (KeyError, ValueError):
                pass

        return viewset_page_size or self.page_size

    def paginate_queryset(self, queryset, request, view=None):
        # Get the page_size from the viewset and then decide which page_size to use
        viewset_page_size = getattr(view, 'page_size', None) 
        page_size = self.get_page_size(request, viewset_page_size)


        # What follows is copy/paste of the code from CursorPagination paginate_queryset method
        if not self.page_size:
            return None

        self.base_url = request.build_absolute_uri()
        self.ordering = self.get_ordering(request, queryset, view)

        self.cursor = self.decode_cursor(request)
        if self.cursor is None:
            (offset, reverse, current_position) = (0, False, None)
        else:
            (offset, reverse, current_position) = self.cursor

        # Cursor pagination always enforces an ordering.
        if reverse:
            queryset = queryset.order_by(*_reverse_ordering(self.ordering))
        else:
            queryset = queryset.order_by(*self.ordering)

        # If we have a cursor with a fixed position then filter by that.
        if current_position is not None:
            order = self.ordering[0]
            is_reversed = order.startswith('-')
            order_attr = order.lstrip('-')

            # Test for: (cursor reversed) XOR (queryset reversed)
            if self.cursor.reverse != is_reversed:
                kwargs = {order_attr + '__lt': current_position}
            else:
                kwargs = {order_attr + '__gt': current_position}

            queryset = queryset.filter(**kwargs)

        # If we have an offset cursor then offset the entire page by that amount.
        # We also always fetch an extra item in order to determine if there is a
        # page following on from this one.
        results = list(queryset[offset:offset + self.page_size + 1])
        self.page = list(results[:self.page_size])

        # Determine the position of the final item following the page.
        if len(results) > len(self.page):
            has_following_position = True
            following_position = self._get_position_from_instance(results[-1], self.ordering)
        else:
            has_following_position = False
            following_position = None

        # If we have a reverse queryset, then the query ordering was in reverse
        # so we need to reverse the items again before returning them to the user.
        if reverse:
            self.page = list(reversed(self.page))

        if reverse:
            # Determine next and previous positions for reverse cursors.
            self.has_next = (current_position is not None) or (offset > 0)
            self.has_previous = has_following_position
            if self.has_next:
                self.next_position = current_position
            if self.has_previous:
                self.previous_position = following_position
        else:
            # Determine next and previous positions for forward cursors.
            self.has_next = has_following_position
            self.has_previous = (current_position is not None) or (offset > 0)
            if self.has_next:
                self.next_position = following_position
            if self.has_previous:
                self.previous_position = current_position

        # Display page controls in the browsable API if there is more
        # than one page.
        if (self.has_previous or self.has_next) and self.template is not None:
            self.display_page_controls = True

        return self.page

注意在上面的例子中 页尺寸 从 request 始终优先于您在代码中设置的任何内容。然后 viewset_page_size 是第二排最后一排 页尺寸 从 Pagination 班级。