Le 23 août 08 à 13:41, Graham Cox a écrit :

I have a class for which equality can be defined as having the same internal string value (which happens to be a UUID-turned-string). I can easily implement isEqual: based on that but the docs say I also need to implement -hash. Any pointers on what is a good way to do that? Could I just safely defer to the -hash returned by the string in question?


Yes, that the way to do it.

To understand what an hash is and how it is used, I suggest you read the hash table article in wikipedia.

http://en.wikipedia.org/wiki/Hash_table

Hash tables are used in Cocoa in NSDictionary, NSSet, NSHashTable, NSHashMap and maybe more. When you understand how it works, choosing the implementation should be obvious.



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