ref – http://quellish.tumblr.com/post/101831085987/implementing-thread-safety-in-cocoa-ios You have just introduced “threads” to your application, because doing everything on the same thread as the UI was starting to noticeably bog things down. At some point you have run into strange crashes or exceptions. Your application no longer behaves as it used to. One problem you have likely introduced is … Continue reading Thread Safety in ios