I'm combining two messages into one, On Feb 24, 2015, at 12:29 AM, random...@fastmail.us wrote:
> On Tue, Feb 24, 2015, at 00:20, Gregory Ewing wrote: >> Cem Karan wrote: >>> I tend to structure my code as a tree or DAG of objects. The owner refers >>> to >>> the owned object, but the owned object has no reference to its owner. With >>> callbacks, you get cycles, where the owned owns the owner. >> >> This is why I suggested registering a listener object >> plus a method name instead of a callback. It avoids that >> reference cycle, because there is no long-lived callback >> object keeping a reference to the listener. > > How does that help? Everywhere you would have had a reference to the > "callback object", you now have a reference to the listener object. > You're just shuffling deck chairs around: if B shouldn't reference A > because A owns B, then removing C from the B->C->A reference chain does > nothing to fix this. On Feb 24, 2015, at 12:45 AM, Gregory Ewing <greg.ew...@canterbury.ac.nz> wrote: > Cem Karan wrote: >> On Feb 22, 2015, at 5:15 AM, Gregory Ewing <greg.ew...@canterbury.ac.nz> >> wrote: >>> Perhaps instead of registering a callback function, you should be >>> registering the listener object together with a method name. >> I see what you're saying, but I don't think it gains us too much. If I store >> an object and an unbound method of the object, or if I store the bound method >> directly, I suspect it will yield approximately the same results. > > It would be weird and unpythonic to have to register both > an object and an unbound method, and if you use a bound > method you can't keep a weak reference to it. Greg, random832 said what I was thinking earlier, that you've only increased the diameter of your cycle without actually fixing it. Can you give a code example where your method breaks the cycle entirely? Thanks, Cem Karan -- https://mail.python.org/mailman/listinfo/python-list
