You could use a metaclass to keep track of all the classes that inherit
from a given one, in a pure Python way it would be something like this
class PluginMeta(type):
# we use __init__ rather than __new__ here because we want
# to modify attributes of the class *after* they have been
# created
def __init__(cls, name, bases, dct):
if not hasattr(cls, 'registry'):
# this is the base class. Create an empty registry
cls.registry = {}
else:
# this is a derived class. Add cls to the registry
interface_id = name.lower()
cls.registry[interface_id] = cls
super(PluginMeta, cls).__init__(name, bases, dct)
class Plugin(object):
__metaclass__ = PluginMeta
So, all the classes that inherit from Plugin are stored in Plugin.registry.
Not sure if it works for mixins though.
On Mon, Oct 31, 2016 at 4:03 PM, Radek Svarz <[email protected]> wrote:
> Hi,
>
> I am using my custom permission mixin on several of my apps's models (not
> all).
>
> For the case when I need to merge from the "old - context" permission to
> the "new - context" permission I want to have function which changes the
> corresponding permission reference attribute in all models, which
> subclassed this mixin.
>
> How do I know which models subclassed this permission mixin and that they
> have the inherited permission reference attribute?
>
> In fact I want to have such function in my mixin:
>
> @classmethod
> def merge_to(cls, from_perm_context, to_perm_context):
>
> perm_context_models = [] # How to get this?
>
> try:
> with transaction.atomic():
> for model in perm_context_models:
> model.objects.filter(
> perm_context=from_perm_context,
> ).update(perm_context=to_perm_context)
> except IntegrityError as e: # or DatabaseError
> raise e
>
>
>
>
> Thanks,
>
> Radek
>
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