On Dec 7, 2011, at 2:07 PM, Julian Berman wrote:
>
> So, when searching, I see some results that seem to ask this question,
> though none of the solutions are for recent versions of sqlalchemy, so,
> I may as well just ask :): how could I have Location.events be
> order_by'd via Event.date?
Well your EventOccurence has "event_name" already there as the primary key
so....order_by=event_name:
location = relationship(Location,
backref=backref(
"event_occurences",
cascade="all, delete-orphan",
order_by=event_name
),
)
If you needed to join out to Event in order to sort, things would be trickier,
but that's not the case here (deleted a crapload of text here because I didn't
notice at first).
Also association_proxy doesn't work usefully with "dynamic" loaders right now.
Tried it, it will let you iterate over the collection but you can't use
order_by(), filter(), or anything like that which is the whole point of using
"dynamic".
>
> Secondly, I haven't been able to find an answer for this, but, I see
> that you can configure the association_proxy to use a dict-like
> structure, but it's always keyed by some other unique column on the
> association object.
>
> Example:
> http://www.sqlalchemy.org/docs/orm/extensions/associationproxy.html#simplifying-association-objects
>
> But how could I use the actual other *model* as the key and another
> column on the association object as the value. To make it clearer, I'd
> like:
>>>> some_location.events
> {<Event: Gala Ball> : True, <Event: Other Thing> : False}
>
>>>> some_location["New Event"] = False
>>>> some_location.events
> {..., <Event: New Event> : False}
you can key on any attribute you'd like as illustrated in
http://www.sqlalchemy.org/docs/orm/collections.html#dictionary-collections.
you'd again need to lose the "dynamic" thing as that doesn't support
dictionaries, then set "event" as the attribute in the
attribute_mapped_collection(). For the True/False you'd need the "events"
association proxy probably to refer to "successful".
you of course lose the ordering here as dictionaries aren't ordered.
class Location(Base):
__tablename__ = 'location'
address = Column(Unicode, primary_key=True)
events = association_proxy("event_occurences", "successful")
class EventOccurence(Base):
location = relationship(Location,
backref=backref(
"event_occurences",
cascade="all, delete-orphan",
collection_class=attribute_mapped_collection("event"),
),
)
>
> Where the values are the `successful` column on the association object,
> and the (hypothetical) creator used the event objects as the keys, not
> as the example on that page uses them as the values.
>
>
> Thanks, sorry for being wordy :),
> Julian
>
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