Re: [Pyobjc-dev] UI bindings no longer work for me

[Ronald O. <ron...@ma...>]

On 1 Sep, 2009, at 6:23, Jason Foreman wrote:

> On Aug 31, 2009, at 10:12 PM, Mani Ghasemlou wrote:
>> I have an NSImageView, whose Hidden state is bound to a variable of  
>> my
>> app delegate. Clicking the "Show" button sets this value to False,  
>> and
>> "Hide" sets this value to True.
>>
>> Using Snow Leopard, the NSImageView's Hidden state does not change
>> when clicking these buttons. Using Leopard, the image shows and hides
>> itself depending on the button pressed.
>>
>> Can someone help me understand what I might be doing wrong?
>
>
> I'm sure someone with more PyObjC experience can give you a better  
> answer, but here's my findings:
>
> There seems to be an issue with the way you initialize your app  
> delegate and KVC/KVO.  If you change your calls like  
> "self.hideComputer = False" to "self.setValue_forKey_(False,  
> 'hideComputer')" it starts working.  Similarly, you can override the  
> app delegate's init method, and this seems to setup KVC correctly  
> for the hideComputer field:
>
> class BindingsUITestAppDelegate(NSObject):
>    # hideComputer = ivar('hideComputer')
>    def init(self):
>        self.hideComputer = False
>        return self
>    .... etc
>
>
> I don't have any idea why this is, and am anxious myself to hear an  
> explanation from the gurus.  But in the meantime this might be a  
> suitable workaround for you.

This will be fixed in the next release of PyObjC. A collegue ran into  
the same issue a while back, and it turns out that the machinery that  
should ensure that the right KVO methods are called didn't work  
properly anymore.

There are two workarounds for this:
1) Use setValue_forKey_ (or self._.hideComputer = False)
2) Explicitly call willChangeValueForKey_ and didChangeValueForKey_

I haven't committed the proper fix because the fix is in my SL tree  
and I haven't had time after the SL release to actually commit the  
code. The commit, and the next PyObjC 2.2 beta release, will happen  
sometime this week (the release will probably be done in the weekend).

Ronald
>
>
> Jason
>
>
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