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Confusion About Objective-C's Memory Management (Cocoa)
Hello everyone, There is one thing about Objective-C's memory management that confuses me, which is a returned object's lifetime from methods with names doesn't start with "alloc", "new", "copy", or "mutableCopy". Take this as an example, when using NSBitmapImageRep's representationUsingType:properties: method, it returns an NSData object (reference: https://developer.apple.com/documentation/appkit/nsbitmapimagerep/representation(using:properties:)?language=objc). While testing this out, the NSData seemed to be an owned object (it doesn't get released until the end of the program). From what I understand, this may be an auto-released object which is released at the end of an autorelease pool block. Could someone explain this in more detail? What if I want to release that NSData object before the end of the autorelease pool block? How can I know which object is autoreleased, borrowed, or owned?
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587
Jan ’25
Is this right way to use NSString BytesNoCopy ?
In my project, i am initialising bytes with some character in cpp function, func CreateByteWithVal (), and passing to a function, func CreateNSStringFromCString(_ pPtr : UnsafeMutableRawPointer, _ pLength : Int), in swift using Swift-Cpp interop. CreateByteWithVal () allocates bytes on heap with value "AAAAAAAAAA", also calls swift function CreateNSStringFromCString. And func CreateNSStringFromCString (_ pPtr : UnsafeMutableRawPointer, _ pLength : Int) creates a NSString instance using NSString's BytesNoCopy initialiser using the bytes (pPtr) passed to it in parameter. Cpp code: void CppClass::CreateByteWithVal () { char * bytesForString = (char *) malloc (10); memset (bytesForString, 65, 10); Interop_Swift::CreateNSStringFromCString (bytesForString, 10); } Swift code: public func CreateNSStringFromCString (_ pPtr : UnsafeMutableRawPointer, _ pLength : Int) { let ns_string:NSString = NSString (bytesNoCopy: pPtr, length: pLength, encoding: String.Encoding.utf8.rawValue, freeWhenDone: false) } If we modify the byte values in memory from C++ directly, the NSString instance, which is supposed to be immutable by nature, reflects these changes. Is this approach appropriate, or is there something we're overlooking or need to address? In our project, we are mutating the byte values directly like this, and the changes are being reflected in the NSString instance : memset (bytesForString, 66, 5); Essentially, I want to confirm whether we can use this method to modify values through C++ without directly mutating the NSString instance. For the UI, we'll be reading the NSString instance by creating a native Swift String instance from it, like this: let str:String = ns_string as String Will the value of str remain consistent as long as we ensure that the correct bytes are provided by C++?
2
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654
Dec ’24
Load bundle resources in UI Tests
I want to load images from my bundle, which works fine when running the main app. However this does not work when running UI Tests. I read that the test bundle is not the main bundle when running tests. I try loading the bundle via this snippet: let bundle = Bundle(for: Frames_HoerspielUITests.self) This is my test class wrapped these the canImport statements so it can be added to the main app target and used for getting the correct bundle: #if canImport(XCTest) import XCTest final class Frames_HoerspielUITests: XCTestCase { override func setUpWithError() throws { continueAfterFailure = false } override func tearDownWithError() throws { } @MainActor func testExample() throws { let app = XCUIApplication() app.launch() } @MainActor func testLaunchPerformance() throws { measure(metrics: [XCTApplicationLaunchMetric()]) { XCUIApplication().launch() } } } #else final class Frames_HoerspielUITests { } #endif However while this works when running the main app, it still fails in the UI tests. It is a SwiftUI only app. and I can't add the images to the asset catalog because they are referenced from another location. Any ideas? Thank you
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277
Jul ’25
How swift string is internally managing memory ?
When i create a intance of swift String : Let str = String ("Hello") As swift String are immutable, and when we mutate the value of these like: str = "Hello world ......." // 200 characters Swift should internally allocate new memory and copy the content to that buffer for update . But when i checked the addresses of original and modified str, both are same? Can you help me understand how this allocation and mutation working internally in swift String?
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514
Nov ’24
String functions problems on iOS18
On iOS 18 some string functions return incorrect values in some cases. Found problems on replacingOccurrences() and split() functions, but there may be others. In the results of these functions in some cases a character is left in the result string when it shouldn't. This did not happen on iOS17 and older versions. I created a very simple Test Project to reproduce the problem. If I run these tests on iOS17 or older the tests succeed. If I run these tests on iOS18 the tests fail. test_TestStr1() function shows a problem in replacingOccurrences() directly using strings. test_TestStr2() function shows a problem in split() that seems to happen only when bridging from NSString to String. import XCTest final class TestStrings18Tests: XCTestCase { override func setUpWithError() throws { // Put setup code here. This method is called before the invocation of each test method in the class. } override func tearDownWithError() throws { // Put teardown code here. This method is called after the invocation of each test method in the class. } func test_TestStr1() { let str1 = "_%\u{7}1\u{7}_"; let str2 = "%\u{7}1\u{7}"; let str3 = "X"; let str4 = str1.replacingOccurrences(of: str2, with: str3); //This should be true XCTAssertTrue(str4 == "_X_"); } func test_TestStr2() { let s1 = "TVAR(6)\u{11}201\"Ã\"\u{11}201\"A\""; let s2 = s1.components(separatedBy: "\u{11}201"); let t1 = NSString("TVAR(6)\u{11}201\"Ã\"\u{11}201\"A\"") as String; let t2 = t1.components(separatedBy: "\u{11}201"); XCTAssertTrue(s2.count == t2.count); let c = s2.count //This should be True XCTAssertTrue(s2[0] == t2[0]); } }
6
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493
Feb ’25
Runtime race condition warning when calling PHPhotoLibrary.shared().performChanges async
I have enabled runtime concurrency warnings to check for future problems concerning concurrency: Build Setting / Other Swift Flags: -Xfrontend -warn-concurrency -Xfrontend -enable-actor-data-race-checks When trying to call the async form of PHPhotoLibrary.shared().performChanges{} I get the following runtime warning: warning: data race detected: @MainActor function at ... was not called on the main thread in the line containing performChanges. My sample code inside a default Xcode multi platform app template is as follows: import SwiftUI import Photos @MainActor class FotoChanger{     func addFotos() async throws{         await PHPhotoLibrary.requestAuthorization(for: .addOnly)         try! await PHPhotoLibrary.shared().performChanges{             let data = NSDataAsset(name: "Swift")!.data             let creationRequest = PHAssetCreationRequest.forAsset()             creationRequest.addResource(with: .photo, data: data, options: PHAssetResourceCreationOptions())         }     } } struct ContentView: View {     var body: some View {         ProgressView()             .task{                 try! await FotoChanger().addFotos()             }     } } You would have to have a Swift data asset inside the asset catalog to run the above code, but the error can even be recreated if the data is invalid. But what am I doing wrong? I have not found a way to run perform changes, the block or whatever causes the error on the main thread. PS: This is only test code to show the problem, don't mind the forced unwraps.
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2.3k
Dec ’24
NSDictionary.isEqual(to:) with Swift dictionary compiles on macOS but not on iOS
The following code works when compiling for macOS: print(NSMutableDictionary().isEqual(to: NSMutableDictionary())) but produces a compiler error when compiling for iOS: 'NSMutableDictionary' is not convertible to '[AnyHashable : Any]' NSDictionary.isEqual(to:) has the same signature on macOS and iOS. Why does this happen? Can I use NSDictionary.isEqual(_:) instead?
2
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471
Feb ’25
How to Remove OpaqueTypeErasure from SwiftUI
I am using swiftui lately in my iOS mobile app, The Mobile app already has a pipeline that detect any experimental features and throw an error I am using swift 5 and as you all know SwiftUI is using some of OpaqueTypeErasure utility types like "some" I heard that in swift 6 the OpaqueTypeErasure is not experimental anymore But upgrading the app swift version will be a very long process Also changing the pipeline will be a very long and tiring process So i want to know if there is a way to remove OpaqueTypeErasure from SwiftUI and what is the alternatives for bypassing the error that being thrown from the pipeline
3
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670
Nov ’24
'init(coordinateRegion:interactionModes:showsUserLocation:userTrackingMode:annotationItems:annotationContent:)' was deprecated in iOS 17.0: Use Map initializers that t
I am currently encountering two deprecated errors in my code. Could someone please identify the issues with the code? Errors: 'init(coordinateRegion:interactionModes:showsUserLocation:userTrackingMode:annotationItems:annotationContent:)' was deprecated in iOS 17.0: Use Map initializers that take a MapContentBuilder instead. 'MapAnnotation' was deprecated in iOS 17.0: Use Annotation along with Map initializers that take a MapContentBuilder instead. Code: // MARK: - Stores Map (Dynamic) struct StoresMapView: View { @State private var storeLocations: [StoreLocation] = [] @State private var region = MKCoordinateRegion( center: CLLocationCoordinate2D(latitude: -31.95, longitude: 115.86), span: MKCoordinateSpan(latitudeDelta: 0.5, longitudeDelta: 0.5) ) var body: some View { Map(coordinateRegion: $region, interactionModes: .all, annotationItems: storeLocations) { store in MapAnnotation(coordinate: CLLocationCoordinate2D(latitude: store.latitude, longitude: store.longitude)) { VStack(spacing: 4) { Image(systemName: "leaf.circle.fill") .font(.title) .foregroundColor(.green) Text(store.name) .font(.caption) .fixedSize() } } } .onAppear(perform: loadStoreData) .navigationTitle("Store Locator") } private func loadStoreData() { guard let url = URL(string: "https://example.com/cop092/StoreLocations.json") else { return } URLSession.shared.dataTask(with: url) { data, _, _ in if let data = data, let decoded = try? JSONDecoder().decode([StoreLocation].self, from: data) { DispatchQueue.main.async { self.storeLocations = decoded if let first = decoded.first { self.region.center = CLLocationCoordinate2D(latitude: first.latitude, longitude: first.longitude) } } } }.resume() } }
1
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99
May ’25
Testing the content of a `Task` in a non-async method
Hi, Considering this method I'd like to test: public func play(_ soundFileName: String, shouldLoop: Bool) { Task { await dataSource.play(soundFileName, shouldLoop: shouldLoop) } } Previously, with XCTest we could use an expectation and wait for it to be fulfilled: func test() sut.play("", shouldLoop: false) wait(for: [mockedAudioPlayerDataSource.invokedPlayExpectation]) XCTAssertEqual(mockedAudioPlayerDataSource.invokedPlayCount, 1) With Swift Testing, I am unsure what a unit test looks like.
4
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936
Oct ’24
Timeline refresh issue for widget on ios 18.2
I use AppIntent to trigger a widget refresh, Appint is used on Button or Toggle,as follows var isAudibleArming = false struct SoundAlarmIntent: AppIntent { static var title: LocalizedStringResource = "SoundAlarmIntent" func perform() async throws -> some IntentResult { isAudibleArming = true return .result() } } func timeline( for configuration: DynamicIntentWidgetPersonIntent, in context: Context ) async -> Timeline { var entries: [Entry] = [] let currentDate = Date() let entry = Entry(person: person(for: configuration)) entries.append(entry) if isAudibleArming { let entry2 = Entry(person: Person(name: "Friend4", dateOfBirth: currentDate.adding(.second, value: 6))) entries.append(entry2) } return .init(entries: entries, policy: .never) } The timeline function fires, with entry corresponding to view1 and entry2 corresponding to view2. I expect to show view1 immediately and view2 6 seconds later. You get the correct response on iOS17. But the 6 second delay function on the discovery code in iOS18.2 takes effect immediately, view1 flashes, view2 appears immediately instead of waiting 6 seconds to appear.
7
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637
Dec ’24
SwiftData and 'NSKeyedUnarchiveFromData' should not be used to for un-archiving and will be removed in a future release
I get this red warning in Xcode every time my app is syncing to the iCloud. My model has only basic types and enum that conform to Codable so i'm not sure what is the problem. App is working well, synchronization works. But the warning doesn't look good. Maybe someone has idea how to debug it.
2
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892
Dec ’24
Tuple Comparision
I was trying to evaulate let myTuple = ("blue", false) let otherTuple = ("blue", true) if myTuple < otherTuple { print("yes it evaluates") } Ans I got /tmp/S9jAk7P7KW/main.swift:5:12: error: binary operator '<' cannot be applied to two '(String, Bool)' operands if myTuple < otherTuple { My question is why there is no compile time issue in first place where the declaration is let myTuple = ("blue", false) ~~~~~~ something like above
2
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441
Jul ’25
jmp_buf layout for Apple Silicon
Greetings! I am actively working on porting x64 code to Apple Silicon now that the time is nigh and part of the fundamentals of our software is a coroutine library for handling cooperative multitasking of GUI operations on the main thread. I was hoping to get the locations of the stack pointer and frame pointer in jmp_buf so, after setjmp() can redirect them to the primary handling routines in our coroutine library that handles the cooperative scheduling (which replaced and ported the old classic MP routines) which worked for PowerPC, i386 and x64. Any thoughts on where in the jmp_buf these might be located? I didn't see anything in the XNU open source. Any advice would be much obliged instead of having to dive in and re-implement these routines in assembly myself!
7
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355
Aug ’25
Circular Reference Error in Xcode 26
I have my project running perfectly fine on Xcode 16. However, in Xcode 26 it doesn't build due to an error that I do not understand. I have three files that pertain to this error: // FriendListResponse.swift import Foundation struct FriendListResponse: Decodable { var friendships: [Friendship] var collections: [FriendCollection] } // Friendship.swift import Foundation struct Friendship: Decodable { var createdAt: String var friendId: Int var friendUserId: Int // user ID of the friend var friendUsername: String var id: Int var tagNames: [String] } // FriendCollection.swift struct FriendCollection: Decodable { var id: Int var permalink: String var tagNames: [String] var title: String } On the first file, FriendListResponse.swift, I am the simple error message "circular reference." I do not understand how these self-contained structs could create a circular reference. Although I have other data types in my project, none of them are even referenced in these files except for Friendship and FriendCollection. The FriendListResponse is a struct that is created from JSON values that are fetched from an API. This is the function that fetches the JSON: public static func listFriends(username: String) async throws -> [Friendship] { let data = try await sendGETRequest( url: "people/\(username)/friends/list.json" ) print(String(data: data, encoding: .utf8)!) let decoder = JSONDecoder() decoder.keyDecodingStrategy = .convertFromSnakeCase let wrapper = try decoder.decode(FriendListResponse.self, from: data) return wrapper.friendships } // Note: the function sendGETRequest is just // a function that I have created that takes a set // of parameters and returns a data object // using the HTTP GET protocol. I don't think // that it is related to this issue. However, if you // think that it is, I can share the code for that. This error has also happened in a few other cases within contained networks of my data structure. I do not know why this error is only appearing once I launch Xcode 26 beta with my project files. I would think that this error also would appear in Xcode 16.4. Any help would be greatly appreciated in my process to compile my project on Xcode 26!
7
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303
Jun ’25
Implementing RawRepresentable for a DictionaryType has broken my Test target build. Not sure how to fix things...
For my app I've created a Dictionary that I want to persist using AppStorage In order to be able to do this, I added RawRepresentable conformance for my specific type of Dictionary. (see code below) typealias ScriptPickers = [Language: Bool] extension ScriptPickers: @retroactive RawRepresentable where Key == Language, Value == Bool { public init?(rawValue: String) { guard let data = rawValue.data(using: .utf8), let result = try? JSONDecoder().decode(ScriptPickers.self, from: data) else { return nil } self = result } public var rawValue: String { guard let data = try? JSONEncoder().encode(self), // data is Data type let result = String(data: data, encoding: .utf8) // coerce NSData to String else { return "{}" // empty Dictionary represented as String } return result } } public enum Language: String, Codable, { case en = "en" case fr = "fr" case ja = "ja" case ko = "ko" case hr = "hr" case de = "de" } This all works fine in my app, however trying to run any tests, the build fails with the following: Conflicting conformance of 'Dictionary<Key, Value>' to protocol 'RawRepresentable'; there cannot be more than one conformance, even with different conditional bounds But then when I comment out my RawRepresentable implementation, I get the following error when attempting to run tests: Value of type 'ScriptPickers' (aka 'Dictionary<Language, Bool>') has no member 'rawValue' I hope Joseph Heller is out there somewhere chuckling at my predicament any/all ideas greatly appreciated
1
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535
Feb ’25
Bridging Headers is unsupported or Module compiled with Swift 5.5.1 cannot be imported by the Swift 5.6 complier
Hello guys! I faced a problem with building... My device suddenly updated to iOS 15.4.1, my Xcode was 13.2 and I had to update it to the latest version (13.3.1) to build the app. After the update, I had a few problems which were successfully solved but one of them stopped me for a few hours. The problem is with Bridging Headers or Swift Compiler, I really don't know what I did badly, and what causes problems. On several forums I often read that is important to set: Build Settings &gt; Build Options &gt; Build Libraries for Distribution But in any case it doesn't work, on yes: error: using bridging headers with module interfaces is unsupported on no: (line with import framework SWXMLHash) /Users/blablabla/SSLModel.swift:9:8: error: module compiled with Swift 5.5.1 cannot be imported by the Swift 5.6 compiler: /Users/blablabla2/Build/Products/Debug-iphoneos/SWXMLHash.framework/Modules/SWXMLHash.swiftmodule/arm64-apple-ios.swiftmodule import SWXMLHash It will be important that I use Carthage. What should I do? Clone all 10 frameworks that I use and re-build them with a new Xcode which includes compiler 5.6? That may be a bad solution... Any answers on similar topics don't help..
3
0
2.9k
Jul ’25
Dateformatter returns date in incorrect format
I have configured DateFormatter in the following way: let df = DateFormatter() df.dateFormat = "yyyy-MM-dd'T'HH:mm:ss'Z'" df.locale = .init(identifier: "en") df.timeZone = .init(secondsFromGMT: 0) in some user devices instead of ISO8601 style it returns date like 09/25/2024 12:00:34 Tried to change date format from settings, changed calendar and I think that checked everything that can cause the problem, but nothing helped to reproduce this issue, but actually this issue exists and consumers complain about not working date picker. Is there any information what can cause such problem? May be there is some bug in iOS itself?
1
0
415
Feb ’25
Swift/C++ interoperability issue in std::string
In scope of one of our project we've faced an issue with constant crashes when integrating C++ library in Swift code using Swift/C++ interoperability. Investigating the root causes of the issue we've discovered that with new version of Swift bug was introduced. Long story short: for strings bigger than 27 symbols memory is feed incorrectly that causes the crashes. By creating this post I wanted to draw community's attention to the problem and promote it to be solved quicker as for now it is not addressed.
1
0
514
Jul ’25