Hi Jonathan,
Rather than create a specific backref for each subtype of deal, why
not just continue with your basic 'deals' backref, then attach regular
python properties to your Merchant class which return just the desired
"sub-deals".
Something like:
class Merchant(object):
...
@property
def available_deals(self):
return [deal for deal in self.deals if deal.available]
@property
def expired_deals(self):
return [deal for deal in self.deals if deal.expired]
... and so on.
You could also reverse your order of definition, define Deal first
with no reference to Merchant, then define Merchant second, with
mapper properties for each of your type of deal (probably mapped to
select statements). But I don't know if it would work to have each of
those different mapper properties all use 'merchant' (with, of course,
the uselist=False option to make it 1:1) as the backref identifier.
On Nov 10, 11:19 am, Jonathan Gardner <jgard...@jonathangardner.net>
wrote:
> I have two tables, merchants and deals. The merchants table is
> represented by Merchant and deals table by Deal.
>
> Each merchant can have 0, 1, or many deals. Some of those deals will
> be available, while others will be expired or coming soon or deleted.
> Each deal belongs to exactly one merchant.
>
> I'd like to setup Merchant to have attributes "deals",
> "available_deals", "expired_deals", "upcoming_deals", and
> "deleted_deals". These would return, obviously, deals from those
> groups.
>
> The twist is that I've spread out my tables and ORM classes across
> several files. I've tried to keep it so that I don't have circular
> dependencies. That means I've defined Merchant first, and then Deal
> later, in separate files
>
> It looks like this:
>
> in model/merchant.py:
> merchants = Table(...)
> class Merchant(object): ...
> mapper(Merchant, merchants)
>
> in model/deal.py:
> deals = Table(...)
> class Deal(object): ...
> mapper(Deal, deals, properties=dict(
> merchant=relationship(Merchant, backref='deals'),
> ))
>
> What can I sprinkle in model/deal.py's mapper call to add backrefs to
> 'available_deals', 'deleted_deals', etc...?
>
> Or am I going about this all wrong?
>
> Thanks in advance. BTW, SQLAlchemy is, by far, the most superior ORM
> in the history of the world, bar none, IMHO.
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