Re: [Pyobjc-dev] KV Observers caused Abort Trap (or: when to remove them)

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

On Apr 6, 2005, at 12:49 AM, Clive Jevons wrote:

> On 6 Apr 2005, at 09:43, Bob Ippolito wrote:
>
>>
>> On Apr 6, 2005, at 12:25 AM, Clive Jevons wrote:
>>
>>> In one of the apps I'm writing I use KVO in order to track when a 
>>> property of a data object is changed so that I can mark it dirty. 
>>> That part works really nicely - in the init() method of the object, 
>>> I attach an observer (itself) for each property which is stored in 
>>> the DB. Everything worked fine until I re-loaded the data, or 
>>> deleted an object. Then the whole thing would crash out without 
>>> giving any hint or sign as to why. As the KVO was the only thing I'd 
>>> changed, I knew it had to be that. After a quick think, I figured it 
>>> was because I hadn't detached them before releasing all references 
>>> to the object in python, and that there were probably invalid 
>>> pointer or references hanging around in the Objective-C part 
>>> responsible for KVO. Once I added calls to 
>>> removeObserver_forKeyPath_ in all the appropriate places everything 
>>> was fine again.
>>>
>>> I *did* try to do the removing of the observers in the dealloc 
>>> (which told me I wasn't to use that method) and the __del__ ... but 
>>> the latter wasn't called before the app bombed out with an 'Abort 
>>> Trap'.
>>>
>>> The solution I currently have works, but I find the code quite 
>>> untidy - on the whole, the reason I love Python is that it enables 
>>> me to express a solution to a problem without loads of technical 
>>> grunt work - like memory management - so having to intersperse KVO 
>>> cleanup code with my business code is really going against the grain 
>>> :( ... can anyone suggest a cleaner solution to this?
>>
>> If you post a simple runnable example that breaks, I'll look into it.
>>
> Can I post TGZs to the list (I'll probably have to include a nib for 
> the example) or do I have to post it to a web site and then post the 
> link to the list?
>

I don't believe the list would like tgz files, but you can either post 
them somewhere or send it to me off-list.  If you post them somewhere, 
someone else might have a chance to answer your question, so that's 
definitely the better option -- but either works.

-bob