将OrderedDict用于SQLAlchemy relationship()？

Question

是否可以告诉SQLAlchemy将OrderedDict用于relationship存储？我只熟悉attribute_mapped_collection，但这是无序的。

Answer 1

在文档中有这样的一个示例：

from sqlalchemy.util import OrderedDict
from sqlalchemy.orm.collections import MappedCollection

class NodeMap(OrderedDict, MappedCollection):
    """Holds 'Node' objects, keyed by the 'name' attribute with insert order maintained."""

    def __init__(self, *args, **kw):
        MappedCollection.__init__(self, keyfunc=lambda node: node.name)
        OrderedDict.__init__(self, *args, **kw)

用法很简单：

foo = relationship(..., collection_class=NodeMap)