Re: Getting added object with KVO

FROM : Hannes Petri
DATE : Mon Jul 17 11:19:38 2006

On 17 jul 2006, at 11:18, Hannes Petri wrote:

> Hello, I'm here again. After some responses, it was rather clear 
> that what I tried to do isn't working. But I haven't given up yet, 
> and now the problem is a little different.
>
> I've found this message:
> http://www.cocoabuilder.com/archive/message/cocoa/2004/12/1/122701
>
> I've created a wrapper around the array that i call 
> CollectionsManager. This is the source code for it:
>
> - (id)init
> {
>     if (self = [super init])
>     {
>         collections = [[NSMutableArray alloc] init];
>         return self;
>     }
>     return nil;
> }
>
> - (void)insertObject:(id)object inCollectionsAtIndex:(int)index
> {
>     [self didChange:NSKeyValueChangeInsertion valuesAtIndexes:
> [NSIndexSet indexSetWithIndex:index] forKey:@"collections"];
>     [collections insertObject:object atIndex:index];
>     [self didChange:NSKeyValueChangeInsertion valuesAtIndexes:
> [NSIndexSet indexSetWithIndex:index] forKey:@"collections"];
> }
>
> - (void)removeObjectFromCollectionsAtIndex:(int)index
> {
>     [self willChange:NSKeyValueChangeRemoval valuesAtIndexes:
> [NSIndexSet indexSetWithIndex:index] forKey:@"collections"];
>     [collections removeObjectAtIndex:index];
>     [self didChange:NSKeyValueChangeRemoval valuesAtIndexes:
> [NSIndexSet indexSetWithIndex:index] forKey:@"collections"];
> }
>
> - (NSMutableArray *)collections
> {
>     return collections;
> }
>
> - (int)countOfCollections
> {
>     return [collections count];
> }
>
> - (CCICollection *)objectInCollectionsAtIndex:(int)index
> {
>     return [collections objectAtIndex:index];
> }
>
> As you can see, it implements the indexed accessors methods. I 
> observe it like this:
>
> [collectionsManager addObserver:collectionsView 
> forKeyPath:@"collections"
>     options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld
>     context:NULL];
>
> The thread says that what I wanted from the beginning (see original 
> message below) should work by doing this way. But it don't. What am 
> I doing wrong this time? I've tried a lot now, but i cant find the 
> solution.
>
> I would be very, very grateful if someone could help me.
>
>
> Hannes Petri
> <email_removed>
>

>> Hello!
>> I'm using KVO to observe an array controller, and when an object 
>> is added, a view should be changed.
>> Now I want a pointer to the object that was added. How should I do?
>> Apples documentation says that I should get the index of the new 
>> object, by querying the changes-dict with the key 
>> NSKeyValueChangeIndexesKey, but that returns null.
>> What am I doing wrong? Is it possible to achieve what I want?
>>
>>
>> Hannes Petri
>> <email_removed>
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>