On a second thought.... why is this not supported?
Because I am not convinced this is a good idea.
If every record of table A only references one record of table B and
vice versa then perhaps there should be only one table AB.
If this is a one (A) to many (B) relation then A cannot contain a
reference to B because would not be unique.
If this is a many to many then there should be a link table. In your
case:
db.define_table('ports',
Field('name','string')
)
db.define_table('agents',
field('name','string')
)
db.define_table('port_agents',
Field('port_id', db.ports),
Field('agent_id',db.agents)
)
It is also possible that I do not understand the problem you are
working on and I am completely wrong.
Massimo
On Oct 8, 8:13 am, mdipierro <[email protected]> wrote:
> Thank you Markus,
>
> technically they are not allowed but you can do with a trick
>
> db.define_table('ports',
> Field('name','string'),
> Field('port_agent_id','integer')
> )
> db.define_table('port_agents',
> field('name','string',
> Field('port_id', db.ports),
> )
> db.ports.port_agent_id.requires=IS_IN_DB(db.'port_agents.id','%(name)
> s')
> db.port_agents.port_id.requires=IS_IN_DB(db.'ports.id','%(name)s')
>
> The port_agent_id reference would not be enforced by the database but
> by web2py. On cascade delete would not work. Everything else would.
>
> On Oct 8, 3:59 am, Markus Schmitz <[email protected]> wrote:
>
> > Hi everybody,
>
> > After evaluating quite a number of web frameworks, I ended up with
> > web2py and frankly I am more than impressed. It rocks in many ways
> > (could talk about it for some time really) and fits very close to my
> > internal requirements.
>
> > But I am a newbee and I am running into newbee problems:
>
> > While creating the needed data model, I got stuck with a circular
> > reference, which I can not resolve. This might be simply a problem
> > with a bad design of my data model, but I will describe it anyway.
>
> > I have port_agents, which are assigned to specific ports. One port
> > might have several port_agents.
> > At the same time each port might have a preferred agent, so my model
> > looks something like this:
>
> > db.define_table('ports',
> > Field('name','string'),
> > Field('port_agent_id','references port_agents') # this references
> > ahead and does not work
> > )
>
> > db.define_table('port_agents',
> > field('name','string',
> > Field('port_id', db.ports),
> > )
>
> > How can this be done in web2py?
>
> > I could use a field 'is preferred agent' on the port agent, but then I
> > have to build checks, that nobody else is a preferred agent for this
> > port etc.
>
> > Any suggestions?
>
> > Regards
>
> > Markus
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