PolyModel enables true polymorphic behavior when querying objects
whose classes are derived from other classes.
So, in the retrieved instance, all fields of all classes at and above
the target class are available to the retrieved instance.
When PolyModel is not used as the base class, then the query only
returns the attributes of the queried class.
Attributes of inherited classes are uninitialized.
So using PolyModel as the base class, the web2py DAL classes can carry
along GAE-specific attributes in base classes,
one of the most useful being the Reference attribute, which will link
together related instances so that GAE will return them in a single
query.
Also, Reference gives automatic bidirectional links.
On Aug 2, 1:17 pm, mdipierro <mdipie...@cs.depaul.edu> wrote:
> What is PolyModel? How is different than what DAL already does when
> running on GAE?
>
> On Aug 2, 11:33 am, dlypka <dly...@gmail.com> wrote:
>
>
>
> > I just got an experimental version of T3 to work with the PolyModel
> > base class in GAE.
> > That gives inherited Classes.
> > So GAE is Quite Amazing.
>
> > I almost have my own DALnr ('nr' = non relational) for web2py working
> > with GAE now.
> > It is using my 'Phantom' Field concept (special table fields in a
> > db.define_table(...) which do native GAE operations but are not
> > otherwise part of the list of columns for that web2py table)
>
> > In particular I got PolyModel to work together with the Reference
> > feature which links together the related entities so that GAE loads
> > them ***ALL*** in a
> > single datastore query.
>
> > In theory, my DALnr will allow creating web2py models which will work
> > on both SQL and GAE and will automatically use 'nr' GAE native
> > features if on GAE.
>
> > ToDo: I still have to generalize my DALnr code.
>
> > My first application of this DALnr is to a high performance TreeView
> > control which loads all branches of a given level in PARALLEL using
> > async multi simultaneous Ajax callbacks.
>
> > On Aug 2, 11:34 am, Pynthon <forumx...@gmail.com> wrote:
>
> > > IMO GAE is too difficult :P.
>
> > > On 2 aug, 07:02, Bottiger <bottig...@gmail.com> wrote:
>
> > > > Google has sunk too much time and effort into adapting Django to
> > > > recommend another framework. They also need to attract more users to
> > > > GAE which Django has plenty of.
>
> > > > On Aug 1, 3:12 pm, mdipierro <mdipie...@cs.depaul.edu> wrote:
>
> > > > > Yes, if only they'd understand we support GAE better than Django does.
> > > > > Our DAL and our appadmin work on GAE, the Django ORM and Django admin
> > > > > do not as far as I know.
>
> > > > > Massimo
>
> > > > > On Aug 1, 3:10 pm, Pynthon <forumx...@gmail.com> wrote:
>
> > > > > > Watch
> > > > > > this:http://googleappengine.blogspot.com/2009/05/web2py-support-new-datast...
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