[openstack-dev] [Solum] Some initial code copying for db/migration
jaypipes at gmail.com
Tue Nov 19 00:09:12 UTC 2013
On 11/18/2013 04:58 PM, Christopher Armstrong wrote:
> On Mon, Nov 18, 2013 at 3:00 PM, Dan Smith <dms at danplanet.com
> <mailto:dms at danplanet.com>> wrote:
> Sorry for the delay in responding to this...
> > * Moved the _obj_classes registry magic out of ObjectMetaClass
> and into
> > its own method for easier use. Since this is a subclass
> based implementation,
> > having a separate method feels more appropriate for a
> > pattern.
> This is actually how I had it in my initial design because I like
> explicit registration. We went off on this MetaClass tangent, which buys
> us certain things, but which also makes certain things quite difficult.
> Pros for metaclass approach:
> - Avoids having to decorate things (meh)
> - Automatic to the point of not being able to create an object type
> without registering it even if you wanted to
> Cons for metaclass approach:
> - Maybe a bit too magical
> - Can make testing hard (see where we save/restore the registry
> between each test)
> - I think it might make subclass implementations harder
> - Definitely more complicated to understand
> Chris much preferred the metaclass approach, so I'm including him here.
> He had some reasoning that won out in the original discussion, although
> I don't really remember what that was.
> It's almost always possible to go without metaclasses without losing
> much relevant brevity, and improving clarity. I strongly recommend
> against their use.
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