[Pyrex] callback

[Bryan Weingarten]

> > class Myplay:
> >     def status(self, sec, msec):
> >         print sec, msec, self.data
> >         return 1
> >
> >     def play(self, mp3file):
> >         self.data = ('test', 2.0, {1:'one'})
> >         m = xxx.Play(mp3file)
> >         m.status_callback(self.status)
               while(m.play_frame()): pass
> >
> > if __name__ == '__main__':
> >     m = Myplay()
> >     m.play(sys.argv[1])
> >
>
> Your problem here is reference counting again. The
> expression 'self.status' creates a new bound method object every time it
> executes.
> m.status_callback must increment the reference count on the callback
> parameter otherwise the bound method created by 'self.status' will be
> destroyed as soon as the call the status_callback returns.  The nested
> function version is probably working more by luck than anything else.
>
> So long as you only have one callback per Play object you could just save
> the callback in the Play object, that way it will be kept alive just as
> long as you need it. Something like:
>
> class Play:
>     def status_callback(self, callback):
>         set_status_callback(self.ctx, _callback_wrapper, <void*>callback)
>         self.callback = callback
>
> -- 
> Duncan Booth                                             duncan at rcp.co.uk

i've added a line to my program above.... maybe this will give you more of a
hint as to why i'm crashing... everytime m.play_frame() is called, status is
called once.

this way seems to grind my computer a bit before it crashes. status never
gets called

 class Play:
     def status_callback(self, callback):
         set_status_callback(self.ctx, _callback_wrapper, <void*>callback)
         self.callback = callback


this way crashes immediately. again, status never gets called

 class Play:
     def status_callback(self, callback):
         Py_INCREF(callback)
         set_status_callback(self.ctx, _callback_wrapper, <void*>callback)

both ways still work for a nested status function in the python code.

bryan