Dexterity类型的反向引用RelationList

Question

我已经创建了两种灵活类型: lab_equipment.py和class_activity.py。class_activity类型包含与lab_activity类型的以下关系：

class_activity.py：

class IClassActivity(form.Schema, IImageScaleTraversable):
[...]
    dexteritytextindexer.searchable('apparatus')
    apparatus = RelationList(
        title=_(u"Apparatus"),
        description=_(u"Choose equipment used in this activity"),
        value_type=RelationChoice(
            source=ObjPathSourceBinder(
                object_provides=ILabEquipment.__identifier__,
                navigation_tree_query= {'path': {'query':'/Plone/ug-demos/equipment'}},
            ),
        ),
    )

[...]

现在，我需要在lab_equipment页面模板中列出class_activity类型的相关成员。

有没有办法将RelationList从class_activity类型反向引用到lab_activity类型，然后将该列表显示到页面模板中？

Answer 1

要检索反向引用(所有使用指定属性指向特定对象的对象)，您不能简单地使用from_object或from_path，因为源对象存储在没有获取包装器的关系中。您应该使用from_id和helper方法，这两个方法在IntId目录中搜索对象。

from Acquisition import aq_inner
from zope.component import getUtility
from zope.intid.interfaces import IIntIds
from zope.security import checkPermission
from zc.relation.interfaces import ICatalog


def back_references(source_object, attribute_name):
    """ Return back references from source object on specified attribute_name """
    catalog = getUtility(ICatalog)
    intids = getUtility(IIntIds)
    result = []
    for rel in catalog.findRelations(
                            dict(to_id=intids.getId(aq_inner(source_object)),
                                 from_attribute=attribute_name)
                            ):
        obj = intids.queryObject(rel.from_id)
        if obj is not None and checkPermission('zope2.View', obj):
            result.append(obj)
    return result

请注意，此方法不检查生效和过期日期或内容语言。

在您示例中，您需要从实验室设备浏览器视图的某些方法中调用此方法，并将反向引用对象列表传递给模板。例如：

class LabEquipmentView(BrowserView):

    def aparatus_backrefs(self):
        return back_references(self.context, 'apparatus')

附言:我从我自己的灵巧问题#234中抄袭了答案，我前段时间发布了：http://code.google.com/p/dexterity/issues/detail?id=234&colspec=ID%20Type%20Status%20Priority%20Difficulty%20Milestone%20Owner%20Summary