Question

使用TreeManager遇到一个奇怪的问题

这是我的代码：

# other imports
from mptt.models import MPTTModel, TreeForeignKey
from mptt.managers import TreeManager

class SectionManager(TreeManager):
    def get_queryset(self):
       return super().get_queryset().filter(published=True)

class Section(MPTTModel):
    published = models.BooleanField(
    default=True,
    help_text="If unpublished, this section will show only"
              " to editors. Else, it will show for all."
)

    objects = TreeManager()
    published_objects = SectionManager()

当我测试它时。我得到以下正确结果：

# show all objects
Section.objects.count()  # result is correct - 65
Section.objects.root_nodes().count() # result is correct - 12

# show published objects, just one is not published.
Section.published_objects.count() # result is correct - 64
Section.published_objects.root_nodes().count()  # result is corrct - 12

但其中一个根的子代尚未发布，并且未在结果中显示。这是测试：

for root in Section.objects.root_nodes(): 
    print(f"root_section_{root.id} has {root.get_children().count()} children") 

    # results ...
    root_section_57 has 13 children # correct - 13 items
    # ... more results

for root in Section.published_objects.root_nodes(): 
    print(f"root_section_{root.id} has {root.get_children().count()} children") 

    # results ...
    root_section_57 has 13 children # WRONG - should be only 12 children
    # ... more results

我可能不了解某些内容，或者我遇到了错误？有什么想法吗？

注意：：此问题已发布在django-mptt github问题页面上，网址为https://github.com/django-mptt/django-mptt/issues/689

Answer 1

https://github.com/django-mptt/django-mptt/blob/master/mptt/managers.py

您将覆盖错误的函数调用。 root_nodes()致电._mptt_filter()

    @delegate_manager
    def root_nodes(self):
        """
        Creates a ``QuerySet`` containing root nodes.
        """
        return self._mptt_filter(parent=None)

您的_mptt_filter没有给定的qs。

    @delegate_manager
    def _mptt_filter(self, qs=None, **filters):
        """
        Like ``self.filter()``, but translates name-agnostic filters for MPTT
        fields.
        """
        if qs is None:
            qs = self
        return qs.filter(**self._translate_lookups(**filters))

现在，您需要根据用例进行自定义。

希望可以有所帮助

使用TreeManager时get_children（）方法出现问题。结果错误

1 个答案: