In a message list screen, each cell downloads its profile image asynchronously and caches it in a [String: UIImage] dictionary. With several threads reading and writing at once, it crashes now and then. Why does it crash?
A Swift Dictionary isn't thread safe. If another thread reads while a write is rehashing or swapping the COW buffer, it touches a freed or half-moved buffer and crashes with a bad memory access.
ConcurrencyShort answerBasics
This code gets called from several threads, and count comes out lower than expected. Can…
#lock #actor
CS fundamentals and algorithmsShort answerAdvanced
You need to write an in-memory image cache with LRU eviction yourself. Which data…
#dictionary #nscache
Memory and ARCMultiple choiceAdvanced
In Objective-C you declare @property (atomic) int a; and run self.a = self.a + 1 a…
#thread-safety #lock
NetworkingMultiple choiceBasics
Select all the statements that correctly describe how NSCache differs from Dictionary.
#dictionary #nscache