Qui, 2005-11-10 às 08:15 +0100, "Martin v. Löwis" escreveu: > Gustavo J. A. M. Carneiro wrote: > > OK, but what if it is a subclass of a builtin type, with instance > > variables? What if the PyObject is GC'ed but the ObjC object remains > > alive, and later you get a new reference to it? Do you create a new > > PyObject wrapper for it? What happened to the instance variables? > > Normally, wrappers don't have state. But if you do have state, this > is how it could work: > > 1. Make two Python objects, PyState and PyWrapper (actually, > PyState doesn't need to be a Python object) > PyState holds the instance variables, and PyWrapper just > holds a pointer to a GObject. > 2. When a Python reference to a GObject is created for the > first time, create both a PyState and a PyWrapper. Have > the GObject point to the PyState, and the PyWrapper to > the GObject. Have the PyState weakly reference the > PyWrapper. > 3. When the refcount to the PyWrapper drops to zero, discard it. > 4. When somebody asks for the data in the PyWrapper, > go to the GObject, then to the PyState, and return the > data from there. > 5. When somebody wants a reference to a GObject which already > has a PyState, check the weak reference to find out > whether there is a PyWrapper already. If yes, return it; > if not, create a new one (and weakly reference it). > 6. When the GObject is discarded, drop the PyState as well. > > This has the following properties: > 1. There are no cyclic references for wrapping GObjects. > 2. Weakly-referencing wrappers is supported; if there > are no strong Python references to the wrapper, > the wrapper goes away, and, potentially, the GObject > as well. > 3. The PyState object lives as long as the GObject. > 4. Using "is" for GObjects/PyWrappers "works": there is > at most one PyWrapper per GObject at any time. > 5. id() of a GObject may change over time, if the wrapper > becomes unreferenced and then recreated.
This was my first approach, actually, in patch 4.1 in [1]. Only your property 2 above drove me to try a different approach -- the weakrefs may become invalid while the GObject may still be alive. That's a bit "surprising". Of course, if I could override weakref.ref() for GObject wrapper types, even that could be worked around... ;-) Thanks, [1] http://bugzilla.gnome.org/show_bug.cgi?id=320428 -- Gustavo J. A. M. Carneiro <[EMAIL PROTECTED]> <[EMAIL PROTECTED]> The universe is always one step beyond logic. _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
