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Editorial Team
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Asked: 2026-06-07T14:46:39+00:00

I have the need to uses custom class that I wrote as a key

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I have the need to uses custom class that I wrote as a key in an NSMutableDictionary (A Socket class, in this case.)

In Java when I use a HashMap or TreeMap, the object requires either a hash function or comparator function respectively for the dictionary to operate. In general, dictionaries need to know some way to compare keys.

From what I’ve read in the documentation, it doesn’t look like I have to do this to use NSMutableDictionary though. Is that correct? And if it is, does anyone know how they implemented key comparison?

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  1. Editorial Team

    As long as the key conforms to NSCopying (which NSObject does not, but many things do), it can be used as a key. The key will be copied using copyWithZone:.

    Regarding how this works, it works just as you note in Java. “The object requires either a hash function or comparator function respectively for the dictionary to operate.” Every NSObject implements both hash and isEqual:.

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