Nathan,
I tried my example again today and have to admit that I can't
reproduce the problem, myself.
I had too many windows open last night and was misled.
properties are ok, they don't create a reference (sigh, good)
and I was messing up, because of my reduced vision.
Sorry about this.
cheers - chris
On 30.11.12 03:43, Nathan Smith wrote:
I am very interested in this because I have a PySide application where
my widgets don't die gracefully (and destroyed isn't signalling their
death). I use properties heavily in my code, so I was excited when I
saw your email thinking they were the culprit. However, I just tried
your example using Python 2.7.1 and PySide 1.1.1, and I can't
reproduce the problem. My table prints "destroyed" immediately when I
call del m. Are you sure that "property" creates a reference?
I did verify in my environment that onDestroy must be static to
function correctly.
On Thu, Nov 29, 2012 at 4:40 PM, Christian Tismer
<[email protected] <mailto:[email protected]>> wrote:
Hi friends,
On 11/29/12 6:37 PM, Stephan Deibel wrote:
> Alexey Vihorev wrote:
>> Thanks, nice find, but... I hit the next hurdle trying to go this
>> way. The signal QObject.destroyed(obj) is passing no arguments
>> (probably because obj is already destroyed), so my static
method has
>> nothing to work on. Which kind of devaluates the whole idea, IMHO.
>> And in PyQt4 it*does* pass the object. Even more: in PyQt4 there is
>> no need for static method approach, as it works perfectly with
>> instance methods:
>
> Yea, you would have to bind the necessary data to the callback
like this:
>
> def on_destroy(val1=self.whatever, val2=self.something):
> print 'destroyed'
> self.destroyed.connect(on_destroy)
>
> Whether this is possible or useful in your case is of course
going to
> depend on the details of the code.
>
> Having 'destroyed' be emitted before the object is destroyed and
> getting the object reference as an arg makes more sense to me.
That is
> what PyQt seems to do and it is what QObject does under Qt using
C++,
> so I'd call this a bug in PySide. I've added
> https://bugreports.qt-project.org/browse/PYSIDE-129
This bug is only half of the story:
We had that simple @staticmethod work-around.
But actually, the main reason seems to be that PySide suffers
any reference cycle.
The tiny example again breaks as soon as I add a property:
{code}
from PySide.QtCore import QAbstractTableModel, QObject
class MyModel(QAbstractTableModel):
def __init__(self, *args):
super(MyModel, self).__init__(*args)
self.destroyed.connect(self.onDestroy)
@staticmethod
def onDestroy():
print('destroyed')
@property
def hugo(self):
return 42
m = MyModel()
del m
{code}
Remove the @property, and it works, again.
Rule of thumb:
If you need anything like a property, use a normal Python class
and put your Qt object into it as an attribute. Otherwise your
program will tend to grow in memory ;-)
Stefan, I added this code to your bug report.
cheers - chris
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