CODEWITHSUNDEEP
objective-cnsarraykey-value-observingnsarraycontroller
Anoop Vaidya
Anoop Vaidya

Reputation: 46543

NSArrayController observing its content count

How do I observe the array controller's count?

What I've tried so far:

    //...
    self.array = [[NSMutableArray alloc] init];
    self.arrayController = [[NSArrayController alloc] initWithContent:self.array];

    [self.arrayController addObserver:self
                                  forKeyPath:@"arrangedObjects"
                                     options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld
                                     context:@"self.array"];


    [self.array addObject:@"anoop"];
    [self.array addObject:@"amit"];


    NSLog(@"%ld", [self.arrayController.content count] );

}

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context {

    if( object == self.arrayController) {
           ...
    }
}

My actual requirement is to observe the array count, but since Array is not KVO compliant, I can't do it. Also I do not want to subclass Array and just add one array property to it as shown in other answers. And then I thought of observing array controller.

Any leads will be highly appreciated.

Upvotes: 2

Views: 1433

Answers (1)

Extra Savoir-Faire
Extra Savoir-Faire

Reputation: 6036

In order to observe the count of arrangedObjects, you must specify a collection operator in your key path. The one you want to use is @count.

So instead of using:

arrangedObjects

you should be using

arrangedObjects.@count

Upvotes: 4

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