How to get the key for a given object from an NSMutableDictionary?

iphone nsmutabledictionary
dontWatchMyProfile picture dontWatchMyProfile · May 7, 2010 · Viewed 35.2k times · Source

I have an object which is in an big NSMutableDictionary, and need to find out which key this has. So I want to look up that "table" from both columns. Not only with keys, but also with objects (to get keys). Is that possible?

Answer

Kevin picture Kevin · May 7, 2010

Look to the parent class (NSDictionary)

- (NSArray *)allKeysForObject:(id)anObject

Which will return a NSArray of all the keys for a given Object Value. BUT it does this by sending an isEqual message to each object of the Dictionary so for your large dataset this may not be best performance.

Maybe you need to hold some form of additional indexing structure structure(s) to allow you to locate the objects on some critical values within them, linked to the key without direct object comparison

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