I have an interesting problem that I haven't been able to solve for quite
some time. I keep finding information about association proxies and the
like, but nothing that really helps (or maybe I'm implementing it
incorrectly).
Let's start with this:
class HandledProjectedItemList(list):
def append(self, proj):
proj.projected = True
list.append(self, proj)
item_table = Table("items", saveddata_meta,
Column("ID", Integer, primary_key = True),
Column("itemID", Integer, nullable = False, index = True),
Column("name", String, nullable = False),
Column("timestamp", Integer, nullable = False),
)
projectedItem_table = Table("projectedItem", saveddata_meta,
Column("sourceID", ForeignKey("item.ID"), primary_key = True),
Column("destID", ForeignKey("item.ID"), primary_key = True),
Column("enabled", Integer))
mapper(Item, item_table,
properties = {"projectedItem" : relation(Item,
primaryjoin = projectedItem_table.c.destID ==
item_table.c.ID,
secondaryjoin = item_table.c.ID ==
projectedItem_table.c.sourceID,
secondary = projectedItem_table,
collection_class = HandledProjectedItemList)
})
I have two tables: a `item` table, and a `projectedItem` table. The `item`
table is the main one, and contains information on items. The projected
items table is a self-referential many-to-many relationship to the items
table, where each item may have a collection of other items attached to it.
We use a custom collection class to load this relationship so that we can
modify a special attribute in the Item objects (if they are loaded via this
relationship, they have their `projected` attribute set to `True`).
This works great. But I also want read / write access to that extra
`enabled` column in the relationship table, while maintaining the current
functionality of loading the projected items into this custom collection
class. I haven't found any information on that that helps, or like I said
before, maybe I'm just not using it correctly.
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