objective c - Is it safe to insert multiple different key-value pairs to an NSMutableDictionary simultaneously? -

objective c - Is it safe to insert multiple different key-value pairs to an NSMutableDictionary simultaneously? -

if have multiple threads might want write nsmutabledictionary (i.e. setobject:forkey:) simultaneously, need synchronize on dictionary if can guarantee threads writing different key-value pairs? if yes, can explain how dictionary break?

nsmutabledictionary not thread-safe, need add together synchronization around concurrent writes, around reads might proceed concurrently writes. fact writing different keys not help much: implementation may resize on adding new key, invalidating internal storage has been allocated before.

you may lucky if keys planning write exist in dictionary already, , no concurrent removals going on. however, strongly recommend against approach.

objective-c thread-safety