Re: [GNUe] Categories

[Reinhard Mueller]

Am Son, den 12.09.2004 schrieb Alex King um 1:58:
> When I declare the master detail relationships in the block definition
> as I have in the attached gfd file and run the form, it emtis a
> traceback when I click on the traceback drop-down.  This wasn't really a
> great surprise, because I don't know if this is an intended usage.

Actually it *should* work, but unfortunately selecting an item in a
dropdown does not move the record pointer of the underlying datasource
to the selected record. Therefore, also the query of the new detail
result set does not happen.

> My thoughts for resolving this:
> 
> 1. Hack on gnue to make this work (I'm using the debian sarge gnue
> packages).  Can anyone tell me (a) if this is a sane thing to want to
> do, and (b) where to start looking if it is.

I tried exactly this, and failed. Not that this means something, but at
least I can tell you it's not trivial.

> 2. Have type dropdown triggers impose a condition on the section
> dropdown datasource somehow.   Ie, when a type is selected, perhaps a
> post change trigger on the type field could somehow impose a "where
> type='newtype'" condition on the sql used to select the items for the
> section dropdown.  Can anyone tell me if I can programatically impose a
> condition and re-run the query, and how to do this?

I think there is a POSTCHANGE or ONCHANGE trigger. However, you would
have to remove the master-detail-connection between these two
datasources because this would actually mean doing master-detail
manually.

> 3. Have a datasource not directly tied to a db table, but implemented as
> a python object (list) somehow, and have the type trigger fill the list
> with a db query each time the type object changes.  This option is
> probably the least elegant, but it has a certain amount of appeal
> because I am familiar with python.  Does anyone know if it is possible
> to have an arbtary python object as a datasource, and if so, how?

I'm quite confident that it is not possible unless you write a new
dbdriver (which you most probably won't do).

> 4. Would appserver help me?  The docs are scarce, and I've not taken
> time yet to investigate, so I have no idea myself.

No, this is a misbehaviour in forms. We have similar problems in forms
we use with appserver.

Thanks,
-- 
Reinhard Mueller
GNU Enterprise project
http://www.gnue.org
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
No army can stop an idea whose time has come.
        -- Victor Hugo, 1802-1885

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