On Sat, Feb 21, 2015 at 1:44 PM, Cem Karan <cfkar...@gmail.com> wrote: > In order to inform users that certain bits of state have changed, I require > them to register a callback with my code. The problem is that when I store > these callbacks, it naturally creates a strong reference to the objects, > which means that if they are deleted without unregistering themselves first, > my code will keep the callbacks alive. Since this could lead to really weird > and nasty situations, I would like to store all the callbacks in a WeakSet > (https://docs.python.org/3/library/weakref.html#weakref.WeakSet). That way, > my code isn't the reason why the objects are kept alive, and if they are no > longer alive, they are automatically removed from the WeakSet, preventing me > from accidentally calling them when they are dead. My question is simple; is > this a good design? If not, why not? Are there any potential 'gotchas' I > should be worried about? >
No, it's not. I would advise using strong references - if the callback is a closure, for instance, you need to hang onto it, because there are unlikely to be any other references to it. If I register a callback with you, I expect it to be called; I expect, in fact, that that *will* keep my object alive. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
