A NSDictionary that doesn't copy keys for iPhone 3.0 SDK?

Question

Hello,

I am using NSDictionary as an associated array (i.e, the keys i am using can be any arbitrary objects). One of the very annoying thing about NSDictionary is that it always make a copy of the key and store it. In my scenario, I will later retrieve the keys from the NSDictionary and do some operations with them. The operation happens to depend on the object identity of the keys. Because the keys i retrieved later are copies of the objects i originally used as keys. The later object identity check fails.

My question is, is there any hashtable-like data structure in the iPhone 3.0 SDK that doesn't make copy of the keys? Thank you.

Outdateboy

Answer 1

If you don't want your key to be copied (or even retained), you can use CFDictionary and supply a kCFTypeDictionaryKeyCallbacks or NULL or customized key callbacks.

To check if objects are equal you should use -isEqual: instead of ==.

Answer 2

NSDictionary is toll-free bridged with CFDictionary. So just do:

CFDictionarySetValue((CFDictionaryRef)myMutableDict, key, object);

It's only the Cocoa method that copies the key.