However the buffer duplication due to copy-on-write happens at every iteration. The nonlinear growth you see is due to the fact that the array buffer increases don't occur that often, as the array implementations have a pretty good heuristic for the capacity increase, in order to avoid allocations every time a new element is added. And the bigger the array, the more it takes to duplicate the buffer. And as soon as you mutate that local array, the copy-on-write mechanism triggers a copy of the array buffer, which results into another heap allocation. The problem with your Swift array code, as Alexander pointed out in his comment, is the fact that you create a local copy of the array that is stored into the dictionary. And the new buffer allocation logic should be fairly similar in both Swift and Objective-C. Note that both Swift array and NSMutableArray under the hood kinda do the same things: when they have no more allocated space for new items, they allocate a new buffer. ![]() $ swiftc MutableDictionary2.swift -o MutableDictionarySwift2 -framework Foundation -O Print("Time spent: \(Date().timeIntervalSinceReferenceDate - startDate.timeIntervalSinceReferenceDate)") Swift with NSMutableArray: import Foundation 17:41:17.686 MutableDictionaryObjc Number of elements: 7 $ clang MutableDictionary.m -o MutableDictionaryObjc -framework Foundation -O3 timeIntervalSinceReferenceDate - startDate.timeIntervalSinceReferenceDate) I benchmarked this approach against Objective-C and Swift with NSMutableArrays, and with 1M entries it seems to be 180x slower, and seems to be exhibiting non-linear growth, suggesting that the compiler is not able to sufficiently optimize this, either. However, this seems to be very inefficient. Is there a way to put mutable arrays as values to Swift dictionaries without performance losses? When I was searching around, most approaches seemed to suggest grabbing the array from the dictionary as a var, adding to it, and then setting it back to the dictionary ( example). How to subscribe self on the event of Device Orientation(not interface orientation)?.Best way to update badgeValue of UITabBarController from a UIView.UINavigationBar Appears Under StatusBar.What does the touch/untouch do in xcode?.WebSockets client for Objective-C (preferably iOS compatible).iphone - coredata application directory.iPhone: Update Localizable.strings files using genstrings?.Game Center Finding a Match Programmatically.How can I determine what crashed Mobile Safari?.apply style to range of text with javascript in uiwebview.Ambiguous use of 'sd_setImage(with:placeholderImage:completed:)' with Swift 3.What's the difference between path and URL in iOS?.React Native multi line TextInput, text is centered.How to select item in collectionview programmatically?.Build/run iOS Xcode project from Terminal.Allow only alphanumeric characters for a UITextField. ![]() Add a ActivityIndicator to the bottom of UITableView while loading.FCM Notification in iOS doesn't play sound when received.iOS10 UNNotificationServiceExtension not called.Use for storing data in key, value pairs. Unlike lists, we don’t have to check every item for a match. Looking for a key in a large dictionary is extremely fast. Next time someone calls your function, you can check your dictionary to see if the answer is pre-computed. The arguments could be the key, with the result stored as the value. Let’s say you want to save computing power, and store the result for a function called with particular arguments. A great practical application for dictionaries is memoization. We use dictionaries when we want to be able to quickly access additional data associated with a particular key. Dictionaries themselves are mutable, but, dictionary keys can only be immutable types. The course content is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.ĭictionaries are a useful type that allow us to store our data in key, value pairs.
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