There are two formats for declaring a reference:
....
db.Field('owner', db.other_table) # this must have other_table already
defined, or it is a Python error;
...
db.Field('owner', 'reference other_table') # this is delayed evaluation,
and what you would use to have two tables cross link each other;
On Tue, Jul 21, 2009 at 10:27 PM, JoshuaJ <surely.you.j...@gmail.com> wrote:
>
> It seems that in web2py, if one table is to have a foreign key to
> another table, the target table must be defined first in db.py. Does
> this mean that there is no way to have two tables that link to each
> other?
>
> Specifically: I'm writing a basic multi-user address book application.
> Each user, of course, owns multiple contacts. However, each user
> selects at most one of their contacts as being their identity, the
> contact that represents themselves.
>
> The way I'd do this in a traditional database would be to define a
> "users" table with fields "username" (a string) and
> "primary_contact_id" (foreign key into contacts table); and then a
> "contacts" table with fields "contact_data" (i'm simplifying here) and
> "owner_id" (pointing back into the users table). However, Web2py
> doesn't seem to allow this.
>
> Does anyone have a solution?
>
> (One workaround would be to add an "is_identity" field to each
> contact, but this seems like a nasty kludge, firstly because since it
> will have the value of "no" for the vast majority of contacts, but
> more importantly because it doesn't guarantee data integrity -- a bug
> in the code could leave a user with multiple identities, something
> impossible with the other representation.)
>
> >
>
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