On Jun 9, 2010, at 13:19, Mazen M. Abdel-Rahman wrote:
> I have a view class that observes changes in a model class's array via KVO.
> Unfortunately - when ever the array is updated - the updates are sent to the
> view one at at a time.
>
> In my model class I have the following line:
>
> NSMutableArray * eventsArrayProxy = [self
> mutableArrayValueForKey:@"events"];
> [eventsArrayProxy addObjectsFromArray:appointments];
You could guarantee that there's only a single KVO notification in a case like
this, by doing it the "old-fashioned" way:
NSMutableArray* newEvents = [[self valueForKey: @"events"]
mutableCopy]; // or something equivalent
[newEvents addObjectsFromArray: appointments];
[self setValue: newEvents forKey @"events"]; // or something equivalent
That would produce only a single notification, though of course the
notification wouldn't tell you which array elements had changed.
Getting back to the original problem, I suspect the reason that it's producing
multiple notification arises from your implementation. If you look in
NSKeyValueCoding.h, in the comments immediately preceding the
'mutableArrayValueForKey:' declaration, you'll see that case 2 is flagged as a
potential performance problem.
The solution is therefore to implement indexed accessors (case 1) in your
class. (Or, remove your setter and let KVC access your array variable directly
-- case 3 -- but generally direct instance variable access is something to be
avoided.)
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