Awesome. Thanks for elaborating.
Sanjiv
On Thu, Aug 6, 2009 at 7:38 PM, Ants Aasma<ants.aa...@gmail.com> wrote:
>
> On Aug 6, 4:09 pm, Sanjiv Singh <singhsanj...@gmail.com> wrote:
>> > Also the GeometryDDL and Geometry classes could use some refactoring
>> > to support extensibility of adding new dialects. Probably via a
>> > registry that maps dialects to their geometry implementations. Also,
>> > the GeometryDDL doesn't account for the fact that dialects could be
>> > subclassed.
>>
>> I am not sure I totally understand the solution you are suggesting.
>> Could you elaborate a bit more? Is there some code I could look at
>> that does something similar?
>
> Regular refactoring of if's to a class hierarchy. Create a base
> strategy class that defines the template methods for before-create,
> after-create etc. and then put the DB specific implementations into db
> specific subclasses that can live in the db specific modules.
> (geoalchemy.postgis.PGGeometyDDL etc.) To create the objects use a
> dict to map dialects to GeometryDDL implementations:
>
> ddl_registry = {
> ('sqlalchemy.databases.postgres', 'PGDialect'): PGGeometryDDL,
> ...
> }
>
> def dialect_to_ddl_impl(dialect):
> for cls in type(dialect).__mro__:
> cls_id = cls.__module__, cls.__name__
> if cls_id in ddl_registry:
> return ddl_registry[cls_id]()
> else:
> raise NotImplementedError
>
> This allows other implementers to add their class to the ddl_registry
> and support other databases without changing your code. You could even
> use setuptools entry points to handle the registering part. Something
> like this is in sqlalchemy.engine.url.URL.get_dialect.
> >
>
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