>
> And replace it with something like this:
> class Keyword(Base):
> .... snip (same as before) ....
>
> class Foo(Base):
> .... snip ....
> keywords = generate_many_to_many_for_me('Foo', 'Keyword')
>> there's a recipe for this at this blog post, you might consider building
on it's general example:
http://techspot.zzzeek.org/2011/05/17/magic-a-new-orm/
>> the missing link is to just use mapping events to set things up at the
appropriate time.
Michael,
Your cats are awesome! I remember reading this the day you put it out there,
but I just didn't understand it at the time. I've been going over this and
now I understand it perfectly! Any chance of pulling some of this back into
sqlalchemy? many_to_many alone saves quite a bit of boilerplate code.
The only change I made was to let many_to_many set up default local / remote
columns on the secondary table so you can just do:
class Video(Base):
keywords = many_to_many("Keyword", "video_keyword")
class many_to_many(DeferredProp):
"""Generates a many to many relationship."""
def __init__(self, target, tablename, **kw):
self.target = target
self.tablename = tablename
self.local = kw.get('local')
self.remote = kw.get('remote')
self.kw = kw
def _config(self, cls, key):
"""Create an association table between parent/target
as well as a relationship()."""
target_cls = cls._decl_class_registry[self.target]
local_pk = list(cls.__table__.primary_key)[0]
target_pk = list(target_cls.__table__.primary_key)[0]
if not self.local:
self.local = cls.__tablename__.lower() + "_id"
if not self.remote:
self.remote = target_cls.__tablename__.lower() + "_id"
t = Table(
self.tablename,
cls.metadata,
Column(self.local, ForeignKey(local_pk),
primary_key=True),
Column(self.remote, ForeignKey(target_pk),
primary_key=True),
keep_existing=True
)
rel = relationship(target_cls,
secondary=t,
collection_class=self.kw.get('collection_class', set)
)
setattr(cls, key, rel)
self._setup_reverse(key, rel, target_cls)
Thanks,
Jeff Peck
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