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POKVO on a collection
 

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  1. POKVO on a collection
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    <p>I added a observer to my collection, and observe the count on it</p> <pre><code>[[[JHTaskSave defaults] tasks] addObserver:self forKeyPath:@"count" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:nil]; </code></pre> <p>JHTaskSave is a singleton object and tasks is a JHTaskCollection KVC compliant, when I add an object to my collection:</p> <pre><code>[[[JHTaskSave defaults] tasks] addTask:newTask] </code></pre> <p>The count of tasks changes but the observeValueForKeyPath is not called, I don't understand why</p> <p>Here is my collection class:</p> <pre><code>@interface JHTaskCollection : NSObject &lt;NSFastEnumeration&gt; { NSMutableArray *_tasks; } @property (nonatomic) NSUInteger count; - (id)taskAtIndex:(NSUInteger)index; - (void)addTask:(JHTask *)task; - (void)removeTask:(JHTask *)task; - (void)insertObject:(id)key inTasksAtIndex:(NSUInteger)index; - (void)removeObjectFromTasksAtIndex:(NSUInteger)index; - (void)removeTaskAtIndexes:(NSIndexSet *)indexes; - (NSArray *)taskAtIndexes:(NSIndexSet *)indexes; @end @implementation JHTaskCollection - (id)init { if(self = [super init]) { _tasks = [[NSMutableArray alloc] init]; } return self; } - (NSUInteger)countByEnumeratingWithState:(NSFastEnumerationState *)state objects:(id __unsafe_unretained *)stackbuf count:(NSUInteger)len { return [_tasks countByEnumeratingWithState:state objects:stackbuf count:len]; } - (NSArray *)taskAtIndexes:(NSIndexSet *)indexes { return [_tasks objectsAtIndexes:indexes]; } - (void)insertObject:(id)key inTasksAtIndex:(NSUInteger)index { [_tasks insertObject:key atIndex:index]; } - (void)removeObjectFromTasksAtIndex:(NSUInteger)index { [_tasks removeObjectAtIndex:index]; } - (void)removeTaskAtIndexes:(NSIndexSet *)indexes { [_tasks removeObjectsAtIndexes:indexes]; } - (JHTask *)taskAtIndex:(NSUInteger)index { return [_tasks objectAtIndex:index]; } - (NSUInteger)count { return _tasks.count; } - (void)addTask:(JHTask *)task { [_tasks addObject:task]; } - (void)removeTask:(JHTask *)task { [_tasks removeObject:task]; } @end </code></pre>
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      1. PTAnswer
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    1. USjames075
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    1. This table or related slice is empty.
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    2. PO
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    3. PO
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    1. This table or related slice is empty.
    1. COfrom JHTaskCollection who is a customized NSMutableArray
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    2. CODoes JHTaskCollection subclass NSMutableArray or does each instance have an NSMutableArray?
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    3. COKVO on collection objects works differently. Follow this approach for [KVO on collection](http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/KeyValueCoding/Articles/AccessorConventions.html#//apple_ref/doc/uid/20002174-178830-BAJEDEFB)
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