On Sat, Sep 26, 2009 at 2:50 PM, Sanjiv Singh <[email protected]> wrote:
> On Sat, Sep 26, 2009 at 5:13 PM, Eric Lemoine
> <[email protected]> wrote:
>> Hi
>>
>> (sorry if it's not the proper forum for this discussion, but I know
>> there may interested people listening here :-)
>
> We are all part of the gispython "community", aren't we ;)
>
>>
>> I'd like that MapFish rely on GeoAlchemy, to share code and development.
>>
>> For this, we need that GeoAlchemy reads database geometry values as
>> objects implementing the __geo_interface__.
>>
>> The easiest would be to make GeoAlchemy create Shapely geometry
>> objects. But I don't think it'd be a good idea to make GeoAlchemy
>> depend on Shapely, because Shapely isn't a pure-Python lib.
>>
>> So I've been thinking about adding the boolean option "shape" to
>> GeoAlchemy's TypeEngine (GeometryBase). If this option is true
>> GeoAlchemy will create a Shapely geometry object using
>> shapely.wrk.loads() and will add as a property to the
>> PersistentSpatialElement object.
>>
>> What do you think?
>>
>
> That would be great.
> Is it possible to implement this as a separate package? That would
> ease up dependency management.
Could you elaborate?
See attached patch to understand what I'm suggesting.
--
Eric Lemoine
Camptocamp France SAS
Savoie Technolac, BP 352
73377 Le Bourget du Lac, Cedex
Tel : 00 33 4 79 44 44 96
Mail : [email protected]
http://www.camptocamp.com
diff -r 3ef69b5712ce geoalchemy/geometry.py
--- a/geoalchemy/geometry.py Tue Sep 01 23:21:34 2009 +0530
+++ b/geoalchemy/geometry.py Sat Sep 26 15:44:33 2009 +0200
@@ -24,14 +24,22 @@
def result_processor(self, dialect):
def process(value):
if value is not None:
+ elt = None
if isinstance(dialect, PGDialect):
- return PGPersistentSpatialElement(value)
+ elt = PGPersistentSpatialElement(value)
if isinstance(dialect, SQLiteDialect):
- return SQLitePersistentSpatialElement(value)
+ elt = SQLitePersistentSpatialElement(value)
if isinstance(dialect, MySQLDialect):
- return MySQLPersistentSpatialElement(value)
+ elt = MySQLPersistentSpatialElement(value)
else:
raise NotImplementedError
+ if self.shape:
+ # create a shapely geometry from the value
+ # and add as a property in the spatial
+ # element
+ from shapely.wkb import loads
+ elt.shape = loads(value.decode('hex'))
+ return elt
else:
return value
return process
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