Re: [Pyobjc-dev] Controller Layer

[Bob I. <bo...@re...>]

On Dec 1, 2003, at 8:08 PM, b.bum wrote:

>
> On Dec 1, 2003, at 4:48 PM, Carlos Phillips wrote:
>>> Try adding...
>>>
>>>     def automaticallyNotifiesObserversForKey_(self, aKey):
>>>         return NO
>>>
>>> ... to your class and see if that fixes the problem.  Also, make 
>>> sure you are running pyobjc based on the latest source from CVS -- 
>>> there have been many updates that are 10.3 specific.
>>>
>>> Finally, we should continue this on pyobjc-dev.  I'm really busy @ 
>>> Apple and will likely not have time to answer you in the coming days 
>>> -- but the folks on pyobjc-dev will answer and they are really 
>>> friendly/knowledgeable.
>>
>> Overloading the method did in fact fix the problem. I thought this 
>> might be useful to someone else.
>
> This appears to be because of the method swizzling that occurs because 
> of key-value observing [KVO].   It causes an infinite loop in the 
> bridge.
>
> You can still use KVO, though.  You just need to call...
>
> - (void)willChangeValueForKey:(NSString *)key;
> - (void)didChangeValueForKey:(NSString *)key;
>
> ... or ...
>
> - (void)willChange:(NSKeyValueChange)change 
> valuesAtIndexes:(NSIndexSet *)indexes forKey:(NSString *)key;
> - (void)didChange:(NSKeyValueChange)change valuesAtIndexes:(NSIndexSet 
> *)indexes forKey:(NSString *)key;
>
> ... before/after the value is changed.

Alternatively you can implement the accessors (and make sure that your 
instance variables aren't keyName or _keyName).. here's a snippet of 
something I have:

def KVC(fn):
     n = fn.__name__.split('_')
     if len(n) == 1:
         if n[0].startswith('countOf'):
             return selector(fn, signature=NSArray.count.signature)
     elif len(n) == 2:
         if n[0].startswith('objectIn') and n[0].endswith('AtIndex') and 
not n[1]:
             return selector(fn, 
signature=NSArray.objectAtIndex_.signature)
         elif n[0].startswith('removeObjectFrom') and 
n[0].endswith('AtIndex') and not n[1]:
             return selector(fn, 
signature=NSMutableArray.removeObjectAtIndex_.signature)
     elif len(n) == 3:
         if n[0] == 'insertObject' and n[1].startswith('in') and 
n[1].endswith('AtIndex') and not n[2]:
            return selector(fn, 
signature=NSMutableArray.insertObject_atIndex_.signature)
         elif n[0].startswith('replaceObjectIn') and 
n[0].endswith('AtIndex') and n[1] == 'withObject' and not n[2]:
             return selector(fn, 
signature=NSMutableArray.replaceObjectAtIndex_withObject_)

class PyNNTPConnectionWindowController(NibClassBuilder.AutoBaseClass):
     # this is heavily sliced and diced
     def init(self):
         self._groups = []

     # key value coding compliance for group array

     def groupArray(self):
         return self._groups

     def countOfGroupArray(self):
         return len(self._groups)
     countOfGroupArray = KVC(countOfGroupArray)

     def objectInGroupArrayAtIndex_(self, index):
         return self._groups[index]
     objectInGroupArrayAtIndex_ = KVC(objectInGroupArrayAtIndex_)

     def insertObject_inGroupArrayAtIndex_(self, obj, index):
         self._groups.insert(index, obj)
     insertObject_inGroupArrayAtIndex_ = 
KVC(insertObject_inGroupArrayAtIndex_)

     def removeObjectFromGroupArrayAtIndex_(self, index):
         del self._groups[index]
     removeObjectFromGroupArrayAtIndex_ = 
KVC(removeObjectFromGroupArrayAtIndex_)


and then elsewhere in the code I use 
self.groupsController.addObjects_(...) instead of manually doing the 
notifications.. although in one place I do:
         self.willChangeValueForKey_(u"groupArray")
         del self._groups[:]
         self.didChangeValueForKey_(u"groupArray")

I'm pretty busy working on non-PyObjC stuff so I can't answer too many 
questions about this, but it may help (for something).

-bob