deriving classes from object extensions

[manstey]

Hi,

I am using Python with Cache dbase, which provides pythonbind module,
and intersys.python bind.object types. But I can't create a class based
on this type:

import intersys.python bind
class MyClass(intersy s.pythonbind.ob ject):
pass

gives me the error: TypeError: Error when calling the metaclass bases
type 'intersys.pytho nbind.object' is not an acceptable base type

Can anyone expain if it is possible for me to derive my own class from
the intersys object so as to add my own functionality?

thanks,
matthew

[Calvin Spealman]

Re: deriving classes from object extensions

On 7 Dec 2006 16:12:18 -0800, manstey <manstey@csu.ed u.auwrote:

Hi,
>
I am using Python with Cache dbase, which provides pythonbind module,
and intersys.python bind.object types. But I can't create a class based
on this type:
>
import intersys.python bind
class MyClass(intersy s.pythonbind.ob ject):
pass
>
gives me the error: TypeError: Error when calling the metaclass bases
type 'intersys.pytho nbind.object' is not an acceptable base type
>
Can anyone expain if it is possible for me to derive my own class from
the intersys object so as to add my own functionality?
>
thanks,
matthew
>
--

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>

Sounds like they are following outdated APIs before the new-style
classes. The builtin types have been updated to be compatible with the
newstyle classes, but your example is of an extension type that does
not have such treatment. It simply is not inheritable, because it is
from the era where one could not derive from any builtin types.

The only solution you really have to use delegation instead of
inheritence. Create your class by itself, give it a reference to an
instance of intersys.python bind.object, and have it look for expected
attributes there. To be a little nicer, you could have a special
__getattr__ method to look up unfound attributes on the delegation
object, your intersys.python bind.object instance.

class Delegating(obje ct):
def __init__(self, old_object):
self._old_objec t = old_object
def __getattr__(sel f, name):
return getattr(self._o ld_object, name)

d = Delegating(my_o ld_object)
d.my_old_attrib ute

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