Max Ischenko wrote:
>
> Hi,
>
> If I have two tables related via foreign key how can I tell SA that
> accessing foreign key should fetch related object automatically? By
> default it simply gives me the FK as integer which is not what I want.
>
> Here are my mappers:
>
> wp_users_tbl = Table('wp_users', meta, autoload=True)
> wp_posts_tbl = Table('wp_posts', meta,
> Column('post_author', Integer,
> ForeignKey(wp_users_tbl.c.ID)),
> autoload=True)
>
> mapper(WordpressPost, wp_posts_tbl)
> mapper(WordpressUser, wp_users_tbl, properties={
> 'posts' : relation(WordpressPost),
> })
>
> >>> post = db.select_one(...)
> >>> print post.post_author # prints 123 instead of
> WordpressUser instance
>
> Thanks,
> Max.
You're halfway there with your 'posts' relation. I think if you pass
backref='author' in your relation, then WordpressPost objects will get
an 'author' property which points back to the WordpressUser. Relations
are described more fully here:
http://www.sqlalchemy.org/docs/datamapping.html#datamapping_relations
The property pointing to the WordpressUser instance is separate from the
property containing the foreign key value. If you want the property to
be named 'post_author', you'll need to rename the foreign key
relationship to prevent them clashing. You can either rename your
ForeignKey column, or override the column name as described here:
http://www.sqlalchemy.org/docs/adv_datamapping.html#advdatamapping_prope
rties_colname
Hope that helps,
Simon
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