On Sep 30, 3:06 pm, Michael Bayer <[EMAIL PROTECTED]> wrote:
> On Sep 30, 2008, at 4:59 AM, Nick Murdoch wrote:
>
>
>
>
>
>
>
> >> we have the "wrapper" thing, its the associationproxy. docs are
> >> here:
> >> http://www.sqlalchemy.org/docs/04/plugins.html#plugins_associationproxy
> >> .
>
> >> In this case you'd probably map a class to the user_articles_table
> >> and
> >> use associationproxy to create user.articles against "article id".
>
> > Hi again, thanks for your pointers. I'm still having trouble,
> > unfortunately.
>
> > I now have the following schema set up:
>
> > ------
>
> > users_table = Table('tg_user', metadata,
> > Column('user_id', Integer, primary_key=True),
> > ...)
> > user_articles_table = Table('user_article', metadata,
> > Column('user_id', Integer, ForeignKey('tg_user.user_id')),
> > Column('article_hash', String(32)),
> > )
>
> > def _create_ua_by_article(article):
> > """ A creator function. """
> > return UserArticle(article_hash=article)
>
> > class User(object):
> > ...
> > saved_articles = association_proxy('user_articles',
> > 'article_hash', creator=_create_ua_by_article)
>
> > class UserArticle(object):
> > """ Joining relationship between Users and articles (articles
> > stored elsewhere) """
> > def __init__(self, user=None, article_hash=None):
> > self.user = user
> > self.article_hash = article_hash
>
> > mapper(User, users_table, properties={
> > 'user_articles': relation(UserArticle),
> > })
>
> > mapper(UserArticle, user_articles_table, properties={
> > 'user': relation(User),
> > })
>
> > ------
>
> > Unfortunately this schema won't generate the tables without
> > complaining about no primary key on user_articles, so I made both
> > columns on UserArticle a primary_key which seemed to work okay.
>
> > So, adding articles to the user.saved_articles list seems to work, and
> > the database reflects this, however, trying to remove an article
> > raises an exception: "AssertionError: Dependency rule tried to blank-
> > out primary key column 'user_article.user_id' on instance
> > '[EMAIL PROTECTED]'"
>
> > I've demonstrated this in the following session. If someone could
> > point out where I'm going wrong, I'd be most grateful :)
>
> when entries are removed from User.user_articles, the row has to be
> deleted. So set "cascade='all, delete-orphan'" on the relation() from
> User->UserArticle.
>
> Also, its better if you use a backref for the "user_articles"/"user"
> combination, like so:
>
> mapper(User, users_table, properties={
> 'user_articles':relation(UserArticle, cascade='all, delete-
> orphan', backref='user')
>
> })
Hi Michael,
Thank you very much! That works perfectly :D
Nick
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/sqlalchemy?hl=en
-~----------~----~----~----~------~----~------~--~---
