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Cocoa Programming/Multithreading
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Multithreading in Cocoa is just like multithreading in any other *nix application, but there are a couple things you should know.
Not All Cocoa Objects are Thread-Safe
Mutable objects are pretty much not thread-safe, and you should attempt to avoid them and find an immutable alternative. If none exists, you can use locks to synchronize the access mutable objects across threads.