Re: [Pyobjc-dev] Key Value Observing of lists?

[Orestis M. <or...@or...>]

>> I have a workaround where I surround changes to the list with:
>>
>> self.willChangeValueForKey_("selections")
>> self.selections.append("new selection")
>> self.didChangeValueForKey_("selections")
>>
>> This works fine for now, but gives me the following messages in the
>> Console:
>>
>> *** Ignoring *** addObserver:forKeyPath:options:context: for
>> 'partName' (of <NSTableBinder: 0x3fad90>{object: <NSTableView:
>> 0x3eabc0>, bindings: content=arrangedObjects} with 0 in 0x0).
>>
>>
> I don't think I've seen this before, but I usually use  
> NSMutableArray instances when dealing with KVO.
>
> Could you try to reproduce this problem in small script?  Ideally  
> this would be a unittest testcase, but a GUI program would be fine  
> too.

OK, I've done some further investigation. This probably was a result  
of my confusion about how pyobjc works with KVO.

This was only appearing when the items in the list where actual Python  
objects.

Sample Code:

class Hello(NSObject):
     label = objc.ivar()
     def init(self):
         self = NSObject.init(self)
         self.label = "hello"
         return self

class World(object):
     def __init__(self):
         self.label = "world"

class KVO_ListsAppDelegate(NSObject):
     list = objc.ivar()
     def init(self):
         self = NSObject.init(self)
         self.list = [Hello.alloc().init(), World()]
         return self

     def applicationDidFinishLaunching_(self, sender):
         NSLog("Application did finish launching.")
         self.list[0].label = "goodbye"
         self.list[1].label = "people"
         NSLog("adding value")
         self.willChangeValueForKey_("list")
         self.list.append(Hello.alloc().init())
         NSLog("added value")
         self.didChangeValueForKey_("list")
         NSLog("done")


The log is:

[Session started at 2008-06-01 22:23:18 +0100.]
2008-06-01 22:23:19.786 KVO_Lists[1407:10b] *** Ignoring ***  
addObserver:forKeyPath:options:context: for 'label' (of  
<NSTableBinder: 0x1f2f9e0>{object: <NSTableView: 0x1f178e0>, bindings:  
content=arrangedObjects} with 0 in 0x0).
2008-06-01 22:23:20.029 KVO_Lists[1407:10b] Application did finish  
launching.
2008-06-01 22:23:20.032 KVO_Lists[1407:10b] adding value
2008-06-01 22:23:20.033 KVO_Lists[1407:10b] added value
2008-06-01 22:23:20.035 KVO_Lists[1407:10b] *** Ignoring ***  
removeObserver:forKeyPath: for 'label' (of <NSTableBinder:  
0x1f2f9e0>{object: <NSTableView: 0x1f178e0>, bindings:  
content=arrangedObjects}).
2008-06-01 22:23:20.036 KVO_Lists[1407:10b] done
2008-06-01 22:23:20.049 KVO_Lists[1407:10b] *** Ignoring ***  
addObserver:forKeyPath:options:context: for 'label' (of  
<NSTableBinder: 0x1f2f9e0>{object: <NSTableView: 0x1f178e0>, bindings:  
content=arrangedObjects} with 0 in 0x0).

Notice how there are three objects in there, but only one complaint.  
So I guess Python objects don't play well with KVO at the moment, and  
I should use NSObjects where possible, right?

Regards,
Orestis