Yes, I will try to post and example tonight.
I believe your students will REALLY like this...
Here are a few DALnr snippets till then:
In gql.py
from google.appengine.ext import db as google_db
from google.appengine.ext.db import polymodel as pm # DLypka Mod to
support PolyModel
:
:
class MyGAEBaseTreeLevel(pm.PolyModel): #DLypka Mod
selflinkPrev = google_db.SelfReferenceProperty
(collection_name='selflinksPrev')
selflinkNext = google_db.SelfReferenceProperty
(collection_name='selflinksNext')
class MyGAEBaseTreeLevelSegment(pm.PolyModel): #DLypka Mod This
entity is a child of MyGAEBaseTreeLevel
linkToTreeLevel = google_db.ReferenceProperty(MyGAEBaseTreeLevel,
required=False, collection_name='linksToTreeLevel')
In Method def _select(self, *fields, **attributes):
:
:
# tablename = table.kind() # DLypka commented out for
PolyModel support
tablename = table.class_name() # DLypka Patch for PolyModel
support
In Method def _create(self):
:
:
if self._tablename == 'MyGAEBaseTreeLevel':
self._tableobj = classobj(self._tablename,
(MyGAEBaseTreeLevel, ), myfields)
elif self._tablename == 'MyGAEBaseTreeLevelSegment':
self._tableobj = classobj(self._tablename,
(MyGAEBaseTreeLevelSegment, ), myfields)
elif self._tablename == 'MyGAEBaseTreeItem':
self._tableobj = classobj(self._tablename,
(MyGAEBaseTreeItem, ), myfields)
else:
self._tableobj = classobj(self._tablename,
(google_db.Model, ), myfields)
return None
----------------------------------------------------------------------------------------
In db.py:
# Create a Parent Entity:
myTreeLevelNativeInstance00keys = db.TreeLevel.insertNative(level=0,
name='TreeLevel_01') # I cloned insert() but I return a dict() with
the native ref as well as id
myTreeLevelNativeInstance00 = myTreeLevelNativeInstance00keys
['nativeRef']
myTreeLevelNativeInstance00id = myTreeLevelNativeInstance00keys['id']
rows=db(db.TreeLevel.id > 0).select()
for row in rows:
myTreeLevelInstance00 = row # NOTE: There is only a single row
here, so myTreeLevelInstance00 will be the row we just inserted into
the web2py DAL
myTreeLevelSegmentNativeInstance00_00keys =
db.TreeLevelSegment.insertNative(idTreeLevel =
myTreeLevelNativeInstance00id, level=0, name='TreeLevelSegment_00_01')
myTreeLevelSegmentNativeInstance00_00 =
myTreeLevelSegmentNativeInstance00_00keys['nativeRef']
myTreeLevelSegmentNativeInstance00_00.linkToTreeLevel=myTreeLevelNativeInstance00
# <=== NOTE This is the Interesting part !!! =======
myTreeLevelSegmentNativeInstance00_00.put() # This rewrites (updates)
the entity
links1 = myTreeLevelNativeInstance00.linksToTreeLevel # <=== NOTE:
This is EXTREMELY Interesting!! - this property was AUTOMATICALLY
maintained by the automatic bidirectional nature of the
ReferenceProperty, so that the 'parent' has a list of refs to its
related children, without any explicit code to add them!!!
# links1 is a google.appengine.ext.db.query
# It is a db.Query
# Here you should loop on links1 which is a column on the parent
entity and see what you get
for key in links1:
childref = key # childref is (magically) a TreeLevelSegment which
is a child of TreeLevel
-- End of DALnr Snippets for GAE ---
- Dave Lypka.
On Aug 4, 12:27 am, mdipierro <mdipie...@cs.depaul.edu> wrote:
> Can you show us an example?
>
> On Aug 3, 9:01 am, dlypka <dly...@gmail.com> wrote:
>
>
>
> > 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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