How do I watch for changes made in NSMutableArray or NSMutableDictionary?

Question

I've noticed that the method 'hashcode' for both NSMutableDictionary and NSMutableArray is giving me the hashvalue to be the number of keys irrespective of the value for NSMutableDictionary and number of objects in case of NSMutableArray.

Basically, I want to detect the change in NSMutableDictionary. My dictionary contains key/value pairs as string/NSMutableArray. And I'want to detect the change in dictionary if an item is added/deleted from any of its values.

In case if I go for calculating hash for NSMutableArray which are the values in my dictionary, it's not feasible since there's also a possibility of a different value added and existing deleted in which case simply giving me the number of items are going to remain same but the hash should be different.

Which is the best way to handle such change in dictionary?

Can't you just subclass the dictionary class and override the adding/deleting methods? — Chris Cooper, Mar 31 '11 at 06:41
The dictionary is a [class cluster](http://www.mikeash.com/pyblog/friday-qa-2010-03-12-subclassing-class-clusters.html) so it can’t be easily subclassed. — zoul, Mar 31 '11 at 06:58
Here is a similar question that might help: http://stackoverflow.com/questions/1106862/observing-nsmutabledictionary-changes — Nick Moore, Mar 31 '11 at 08:34

score 1 · Accepted Answer · answered Mar 31 '11 at 08:29

You can retain the original dictionary an test if it is equal to the new one

isEqualToDictionary:

Returns a Boolean value that indicates whether the contents of the receiving dictionary are equal to the contents of another given dictionary.

 - (BOOL)isEqualToDictionary:(NSDictionary*)otherDictionary

Docs here

How do I watch for changes made in NSMutableArray or NSMutableDictionary?

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