Getting hold of a mapper class from within another mapper class?
Andreas Jung
Table 'media' has 1 : N relationship to table 'history'.
class Media(object):
def addHistory(self, comment):
self.history.append(History(....)))
Inside addHistory() I need to get hold of the mapper class History for
'history' in order to append a new items to the media's history.
Unfortunately the complete mappers are hidden behind a wrapper and the
mappers are only available to the application through a dedicated
getMapper() call returning a registered mapper by name. However the wrapper
instance
is not available to the Media mapper itself. Is there a way to get hold
of depending mapper classes - in this case the History mapper - directly
from the Media mapper class (since it knows that it depends on the History
mapper)?
Andreas
Michael Bayer
On May 12, 2007, at 6:58 AM, Andreas Jung wrote:
> I have the following (scary) use-case:
>
> Table 'media' has 1 : N relationship to table 'history'.
>
> class Media(object):
>
> def addHistory(self, comment):
> self.history.append(History(....)))
>
>
> Inside addHistory() I need to get hold of the mapper class History
> for 'history' in order to append a new items to the media's history.
ok, you mean a "mapped" class, right ? i.e.the History class. i
dont exactly understand why you cant just say "History", so heres the
most generic way possible to go from 'self' to the class used on a
relation:
class_mapper(self.__class__).props['history'].mapper.class_
Andreas Jung
--On 12. Mai 2007 11:22:51 -0400 Michael Bayer <mik...@zzzcomputing.com>
wrote:
> ok, you mean a "mapped" class, right ? i.e.the History class. i
> dont exactly understand why you cant just say "History", so heres the
> most generic way possible to go from 'self' to the class used on a
> relation:
Basically this is a limitation (or call it a feature) of z3c.sqlalchemy
where the complete mapper handling is handled through a wrapper which isn't
available in the context of a mapper instance (unless you pass the wrapper
around).
>
> class_mapper(self.__class__).props['history'].mapper.class_
Thanks this works!
Andreas
>
>
>
>
>
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