On Aug 1, 2011, at 8:34 PM, somewhatofftheway wrote:
> Hi,
>
> I'm trying to convert a 'simple' many-to-many relationship to an
> association object in order to allow the relationship to have
> attributes. I've followed the code in examples/association/
> proxied_association.py fairly closely (or so I thought) but it isn't
> working for me.
>
> As an example, let's say I am trying to create a relationship between
> an RSS feed and the pages from the feed but I want a feed_date on the
> relationship. Currently, my code look something like this:
>
> class Page (Base):
> __tablename__ = 'pages'
> id = Column(Integer, primary_key=True)
>
> posts = relationship("Post", cascade="all, delete-orphan",
> backref='pages')
> feeds = association_proxy("feeds", "feed")
>
>
> class Post(Base)
> __tablename__ = 'pages_feeds'
> page_id = Column(Integer, ForeignKey('pages.id'),
> primary_key=True)
> feed_id = Column(Integer, ForeignKey('feeds.id'),
> primary_key=True)
> feed = relationship(Feed, lazy='joined')
>
> I haven't changed the Feed class at all.
>
> When I do something along the lines of:
>
> page = Page()
> feed = Feed()
> page.feeds.append(feed)
>
> the query that is issued is as follows:
>
> IntegrityError: (IntegrityError) pages_feeds.feed_id may not be NULL
> u'INSERT INTO pages_feeds (page_id) VALUES (?)' (1,)
>
> So, clearly I have missed out the part of the config that explains
> that adds in the second foreign key. Could anybody point me to where
> please?
you need a constructor and/or creator that generates Post() with the "feed"
attached to it, like def __init__(self, feed): self.feed = feed, then the assoc
proxy with creator=Post.
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