[ZPatterns] Rack.getItem returning attributeless objects (ZPatterns newbie)

[Steve Spicklemire]

Steve Spicklemire wrote:
> 
> Phillip Crumpler wrote:
> >
> > I tried what you suggested - still no banana :-(  So, I tried an example so
> > simple even I would have trouble getting it wrong.
> >
> > The rack has a single SQL query, SQL_get:
> >   SELECT name FROM dskins WHERE dskin_id=<dtml-sqlvar dskin_id type="int">
> > The table has two columns, dskin_id int and name text.
> > The rack has a single skinscript method, with one line:
> >   WITH QUERY SQL_get(dskin_id=self.id) COMPUTE name

Oh yeah.. this also needs to change to:

WITH QUERY SQL_get(dskin_id=self.id) COMPUTE name, dskin_id

-steve

> > The load attribute of the rack is 'name'. The rack stores a zclass that is
> > derived from DataSkin, with an index_html method added, nothing else.
> >
> > Still, getItem with a non existant dskin_id will return an object. Is this
> > suppposed to happen?
> >
> 
> Is 'name' in a propertysheet of the ZClass? If so.. it won't work! Try this:
> 
> SELECT name, dskin_id FROM dskins WHERE <dtml-sqltest dskin_id type="int">
> 
> set the 'attribute to load' to 'dskin_id'. Make sure that dskin_id is
> *not* in any propertysheet of the ZClass.
> 
> -steve
> 
> > SQL_get is being called correctly and returning nil rows. Digging around a
> > bit in Racky.py,  the line in Rack.retrieveItem
> >         if hasattr(item.aq_base, a):
> > succeeds, even though the query returned no rows (a is the loadAttribute of
> > the Rack, 'name'). getattr(item.aq_base,a) returns an empty string.
> >
> > Help!
> >
> > Phillip
> >
> > > -----Original Message-----
> > > From: Phillip J. Eby [mailto:pje@telecommunity.com]
> > > Sent: Friday, 6 July 2001 2:34 AM
> > > To: Phillip Crumpler; zpatterns@eby-sarna.com
> > > Subject: Re: [ZPatterns] Rack.getItem returning attributeless objects
> > > (ZPatterns newbie)
> > >
> > >
> > > At 12:41 AM 7/6/01 +1000, Phillip Crumpler wrote:
> > > >
> > > > I have a specialist, with the default rack, storing a zclass
> > > derived from
> > > >DataSkin. The rack is set to 'load by accessing attribute: id'.
> > > Within the
> > >
> > > That won't work.  The object already *has* an 'id' attribute, so the
> > > SkinScript that computes it will never be executed.
> > >
> > >
> > > >specialist are a few sql methods: SQL_get, SQL_change, SQL_create,
> > > >SQL_delete. The table has two columns, id (int) and name (text).
> > > The zclass
> > > >has a simple index_html method to show the instance's id and name
> > > >attributes.
> > > >
> > > >The rack has a skinscript method like so:
> > > >
> > > >WITH SQL_get(id=self.id) COMPUTE id, name
> > >
> > > Try making this:
> > >
> > > WITH QUERY SQL_get(id=self.id) COMPUTE name
> > >
> > > And making the 'name' attribute be the "load" attribute.
> > >
> > >
> > >
> > >
> > > >WHEN OBJECT ADDED CALL SQL_create(id=self.id, name=self.name)
> > > >
> > > >WHEN OBJECT CHANGED STORE id, name USING SQL_change(id=self.id,
> > > >name=self.name)
> > > >
> > > >WHEN OBJECT DELETED CALL SQL_delete(id=self.id)
> > >
> > > The rest of this looks fine.
> > >
> > >
> > > >I'm new to skinscript, so I'm not too sure about this. The only
> > > other Data
> > > >Plug-In in the rack is a SpecialistPlugIn (but the Specialist
> > > itself has no
> > > >Data Plug-Ins)
> > > >
> > > >My (first) problem is this: a call to Rack.getItem will _always_
> > > return an
> > > >instance - if SQL_get returns no rows then it just ends up with no
> > > >attributes.
> > >
> > > Right, because the object already has an id.
> > >
> > >
> > > > I could always just get brutal and insert it into the database
> > > directly but
> > > >I think that would really be missing the point ;^)  How do I make
> > > >Rack.getItem return None in this case?
> > >
> > > Change to using a load attribute that's actually dependent on the
> > > result of
> > > the query.
> > >
> >
> > _______________________________________________
> > ZPatterns mailing list
> > ZPatterns@eby-sarna.com
> > http://www.eby-sarna.com/mailman/listinfo/zpatterns