NSMutableDictionary’s Practical Limit
Pro tip: if your Objective-C application deals with a huge collection of objects, avoid relying on NSMutableDictionary as the “count” method returns the number of objects… modulo 0x2000000 “allKeys” and “allValues” are also affected…
Fun fact! If you make your dictionary with 0x2000001 objects in Swift and then cast it to an NSDictionary, then it works just fine from Objective-C. Can’t be a mutable dictionary that way, though.
Update (2018-10-31): Vincent Bénony:
It depends on the private class used by Foundation. For instance, if I build the dictionary with « dictionaryWithObjects:forKeys: » it works perfectly, but as soon as I create a mutable copy, it fails.
