Hi,
I'm having trouble understanding the correct syntax to be used with
Declarative and a column property.
The select statement I'm using is:
select([func.substr(my_table.c.my_string, 2, 3)]).label(my_substr'),
deferred=True
And (as per the docs using the expanded syntax, this works as expected.
With the Declarative syntax, I've tried:
from sqlalchemy.util import classproperty
from sqlalchemy.orm ..., column_property
class MySubstr(object):
@classproperty
def my_substr(cls):
return column_property(
select([func.substr(cls.my_str, 2, 3)]).label('my_substr')
)
class MyTable(Base, MySubstr):
.....
and then expect to be able to call a record in MyTable and return its
"my_substr", however, all I'm getting is a representation of the object ...
eg <sqlalchemy.orm.properties.ColumnProperty object at 0xa4951cc> and no
apparent way of seeing its value.
Should the @classproperty sit within the "MyTable(Base)" itself (ie is there
a need for the separate object -- and have I been confused by the section on
'mixins' )?
I'd be really grateful for any clues!
Many thanks,
Rob
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