Re: KVC and KVO for arrays

FROM : Adam P Jenkins
DATE : Tue Feb 12 23:09:18 2008

NSMutableArray is already KVC and KVO compliant, so you don't need to 
do anything special to use them with bindings.  You only need to 
implement indexed accessor methods if you're writing your own class 
which you'd like to behave like an array with regard to bindings.

On Feb 12, 2008, at 3:32 PM, Hans van der Meer wrote:

> I came along this problem because I understand the binding mechanism 
> requires kvc calls  in order to get the observing going. It is 
> unclear to me how to do this for changes in array. (I did read the 
> KVC and KVO Programming Guides).
>
> Setting an array works, for example:
>
> NSMutableArray *myArray;
> @property(copy) NSMutableArray *myArray;
> @synthesize myArray;
> ....
> myArray = [NSMutableArray arrayWithCapacity:10];
> // fill myArray with objects for ex. with [myArray addObject:..] etc.
> [self setMyArray:myArray]
>
> In the above code the NSArrayController bound to myArray a Model Key 
> Path gets informed of the change.
>
> In the documentation there is mention of "indexed accessor methods" 
> that will directly inform the array of changes. For changes these 
> are given as insertObject:in<Key>AtIndex: and 
> removeObjectFrom<Key>AtIndex:
> The <key> in this case being MyArray.
>
> That sounds fine for implementing array accessing in a custom class 
> of my own. But what for the standard NSArrayMutable array? When 
> coding:
> [myArray insertObject:anObject inMyArrayAtIndex:0]
> the compiler warns me that NSMutableArray does not know this method 
> and on executing I get the more or less expected error: [NSCFArray 
> insertObject:inSolutionsAtIndex:]: unrecognized selector sent to 
> instance.
>
> Is there something I do not see? Or do I have to add all the 
> "indexed accessor methods"  to NSArray and NSMutableArray in a 
> category?
> That generates another question: in that case, must I program for 
> manual observing by bracketing the implementation statements with 
> [self willChangeValueForKey ..etc] messages?
>
> Finally I tried:
> myArray = [[NSMutableArray arrayWithCapacity:10] 
> mutableArrayValueForKey:@"myArray"];
> [myArray addObject:anObject];
> But that did not work either, the NSArrayController not being 
> updated. Though no NSUndefinedKeyException was raised, so 
> mutableArrayValueForKey must have had some effect.
>
> Could someone possibly enlighten me? Thanks in advance.
>
> Hans van der Meer
>
>
>
>
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