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Validity of Pointer Returned by withUnsafePointer During CPU Time Slicing
Hello, I am using the withUnsafePointer API in Swift and have a question regarding the validity of the pointer returned by this API. Specifically, I want to understand if the pointer remains valid if the CPU performs a context switch due to its time-slicing mechanism while the closure is executing. Is the pointer returned by withUnsafePointer guaranteed to be valid throughout the entire execution of the closure, even if a CPU context switch occurs as part of time slicing?
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416
Aug ’24
Performance with large @Published struct
I'm looking at performance around large codable nested structures that come in from HTTP/JSON. We are seeing stalls on the main thread, and after reviewing all the code, the webrequests and parsing are async and background. The post to set the new struct value (80K) is handled on mainthread. When I looked at the nested structures, they are about 80K. Reading several articles and posts suggested that observing structs will cause a refresh on any change. And that large structures will take longer as they have to be copied for passing to each observer. And that more observers will slow things down. So a made a test app to verify these premises. The app has an timer animating a slider. A VM with a structure containing a byte array. Sliders to scale the size of the byte array from 10K to 200K and to scale the number of observers from 1 to 100. It also measures the actual duration between the timer ticks. My intention is to be able to visual see mainthread stalls and be able to measure them and see the average and max frame delays. Using this to test I found little difference in performance given different structure sizes or number of observers. I'm not certain if this is expected or if I missing something in creating my test app. I have also created a variation where the top struct is a an observable class. I see no difference between struct or class. I'm wondering if this is due to copy-on-mutate causing the struct to actually be passed as reference under the good? I wonder if other optimizations are minimizing the affect of scaling from 1 to 100 observers. I appreciate any insights & critiques. #if CLASS_BASED class LargeStruct: ObservableObject { @Published var data: [UInt8] init(size: Int = 80_000) { self.data = [UInt8](repeating: 0, count: size) } func regenerate(size: Int) { self.data = [UInt8](repeating: UInt8.random(in: 0...255), count: size) } var hashValue: String { let hash = SHA256.hash(data: Data(data)) return hash.compactMap { String(format: "%02x", $0) }.joined() } } #else struct LargeStruct { var data: [UInt8] init(size: Int = 80_000) { self.data = [UInt8](repeating: 0, count: size) } mutating func regenerate(size: Int) { self.data = [UInt8](repeating: UInt8.random(in: 0...255), count: size) } var hashValue: String { let hash = SHA256.hash(data: Data(data)) return hash.compactMap { String(format: "%02x", $0) }.joined() } } #endif class ViewModel: ObservableObject { @Published var largeStruct = LargeStruct() } struct ContentView: View { @StateObject var vm = ViewModel() @State private var isRotating = false @State private var counter = 0.0 @State private var size: Double = 80_000 @State private var observerCount: Double = 10 // Variables to track time intervals @State private var lastTickTime: Date? @State private var minInterval: Double = .infinity @State private var maxInterval: Double = 0 @State private var totalInterval: Double = 0 @State private var tickCount: Int = 0 var body: some View { VStack { Model3D(named: "Scene", bundle: realityKitContentBundle) .padding(.bottom, 50) // A rotating square to visualize stalling Rectangle() .fill(Color.blue) .frame(width: 50, height: 50) .rotationEffect(isRotating ? .degrees(360) : .degrees(0)) .animation(.linear(duration: 2).repeatForever(autoreverses: false), value: isRotating) .onAppear { isRotating = true } Slider(value: $counter, in: 0...100) .padding() .onAppear { Timer.scheduledTimer(withTimeInterval: 0.005, repeats: true) { timer in let now = Date() if let lastTime = lastTickTime { let interval = now.timeIntervalSince(lastTime) minInterval = min(minInterval, interval) maxInterval = max(maxInterval, interval) totalInterval += interval tickCount += 1 } lastTickTime = now counter += 0.2 if counter > 100 { counter = 0 } } } HStack { Text(String(format: "Min: %.3f ms", minInterval * 1000)) Text(String(format: "Max: %.3f ms", maxInterval * 1000)) Text(String(format: "Avg: %.3f ms", (totalInterval / Double(tickCount)) * 1000)) } .padding() Text("Hash: \(vm.largeStruct.hashValue)") .padding() Text("Hello, world!") Button("Regenerate") { vm.largeStruct.regenerate(size: Int(size)) // Trigger the regeneration with the selected size } Button("Clear Stats") { minInterval = .infinity maxInterval = 0 totalInterval = 0 tickCount = 0 lastTickTime = nil } .padding(.bottom) Text("Size: \(Int(size)) bytes") Slider(value: $size, in: 10_000...200_000, step: 10_000) .padding() Text("Number of Observers: \(observerCount)") Slider(value: $observerCount, in: 1...100, step: 5) .padding() HStack { ForEach(0..<Int(observerCount), id: \.self) { index in Text("Observer \(index + 1): \(vm.largeStruct.data[index])") .padding(5) } } } .padding() } }
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447
Aug ’24
xcode not showing output
Hi I was using Xcode for c++ (for competitive programming purposes, not sure if this is the standard choice but using it anyway) I included a &lt;bits/stdc++.h&gt; to the include file for XCode.app and they didn't show any error. But then when I ran my code, it showed "Build Succeeded" although no output was visible.
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385
Sep ’24
Undefined symbol: _c2i_ASN1_INTEGER when building my projec for iOS 18
Note that I am trying to build my project for IOS 18 using XCode version 16 Beta 6. I have version 18.0 of the iOS beta installed on my iPhone. My project includes pods for Firebase and GRPC-Core. I ran pod update and it installed Firebase (11.1.0), BoringSSL-GRPC 0.0.36, OpenSSL-Universal 3.3.1000, and gRPC-Core 1.65.5. When I try to build my project I encounter the following error: Undefined symbol: _c2i_ASN1_INTEGER This symbol is not referenced in my code. It's unclear which pod references this symbol - although Firebase is a likely candidate. Is anyone else encountering this issue? I'm wondering if I could safely go back to a version of Firebase that does, as the previous version I had installed (10.22.0) didn't have this issue.
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450
Sep ’24
New open-source package, RJSwiftMacros!
🚀 I am thrilled to announce my latest open-source project, RJSwiftMacros! This Swift package enables developers to enhance efficiency by simplifying code generation and automating repetitive tasks in their projects. 🔥 Here's a glimpse of what you can accomplish with RJSwiftMacros: Generate mock data using @MockBuilder macro. Generate coding keys using @CodingKeys macro. RJSwiftMacros is actively maintained and welcomes contributions! 🤝 🔗 GitHub Repository: https://lnkd.in/dPikQTjD I look forward to your feedback and ideas to further enhance its value for the Swift community. 💻
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Sep ’24
Understanding how ARC is different for Struct vs Class
Hi, I was trying to understand how swift manages it memory just wanted to verify my understanding on it. For Value Types i.e. Struct ARC (Automatic Reference Counting) is not there, Memory is Managed/Confined on the basis of scope of that Variable. And For Struct whenver we do assignment a Copy is been created. For Classes, Swift Manages Memroy with the help of ARC i.e. whenever I create a instance of class its reference count get increased and when we assign same instance to new variable then it also result in increment of Reference Count. The Memory will get deallocated when all the variables pointing to that object are no longer in use.
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382
Aug ’24
How to pass Child Class reference as Parent Class
So I have this child class with a function that creates a perdetermined array of other classes. class DirectGame : GameParent { static func GetAllChallenges() -> Array<ChallengeParent>{ return [LockdownChallenge(game: self)] } } These other classes take in a GameParent class in the initalizer like so: class LockdownChallenge { var game : GameParent init(game: GameParent) { self.game = game } } However this line return [LockdownChallenge(game: self)] is throwing the error "Cannot convert value of type 'DirectGame.Type' to expected argument type 'GameParent'" How do I pass in a reference to DirectGame into the initalizer of ChallengeParent?
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Aug ’24
How ARC works withUnsafeMutablePointer Interface.
I am using withUnsafeMutablePointer to get raw pointer from Data. Once I get a Pointer I follow these steps: I create a Wrapper using that Pointer. After that I increase it ARC and pass it as a opaque to C++ When I was on First Step if my thread get suspended and after some time if it resumes then is there a possibility that the Memory will get freed due to ARC. Adding basic Code Flow depicting what i am doing. public class DataHolder { public init () {} public var data_wrapper : Data? } func InternalReceiveHandler (_ pContent : Data?) -> Void { var holder : DataHolder = DataHolder.init () withUnsafeMutablePointer (to : &pContent) { data_pointer in holder.data_wrapper = Data.init (noBytesCopy : data_pointer, count : no_of_bytes, deallocator : .none) return Unmanaged.passRetained (holder).toOpaque () } } Is there a possibility that when I am creating the wrapper my thread get suspended and when it get resumed the Memory the pointer was pointing can be freed by ARC.
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453
Aug ’24
Can't find Python.h anywhere on Mac
I am trying to embed a python file that uses a python library in c, to do this I need to include python.h but I don't see it anywhere on my mac. Right now when I try to compile I just get a missing Python.h compile error. I tried using the search bar to find it in /usr and /library. Neither had the file. I tried doing #include <Python/python.h> and that doesn't change anything. Is trying to setup a virtual env the issue?
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535
Aug ’24
NIOThreadPool segfault
Following the latest Command Line Tools update, the swift-nio library (https://github.com/apple/swift-nio) causes my program to segfault. The function where the error occurs is runIfActive, which is executed with the following error: Thread 12: EXC_BAD_ACCESS (code=1, address=0x4) swift version: swiftlang-6.0.0.7.6 clang-1600.0.24.1 NIO version: 2.70.0
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Aug ’24
Await expectations with Swift Testing?
I'm used to wait for expectations when using XCTest, but I'm completely stumped by the seemingly-absent option for expecting some parts of my code to be called in Swift Testing 🤔 Consider the following: protocol MyAPI { func getData() async throws -> String } class MockAPI: MyAPI { let stub: () async throws -> String init(stub: @escaping () async throws -> String = { "hello" }) { self.stub = stub } func getData() async throws -> String { try await stub() } } Which is being used in my view model: class MyViewModel: ObservableObject { private let api: MyAPI @Published var data: String init(api: MyAPI) { self.api = api } func refresh() async throws { self.data = try await api.getData() } } When I wrote tests in the past, I would simply override the stub of the MockAPI implementation and fulfill an expectation in there: class MyViewModelTests: XCTestCase { func testModelCallsAPIOnRefresh() async throws { let expectCallsAPI = expectation("Model should call API") let api = MockAPI { expectCallsAPI.fulfill() return "hello" } let model = MyViewModel(api: api) try await model.refresh() await fulfillment(of: [expectCallsAPI], timeout: 1) } } How would I go about checking that my model does indeed call the API when using Swift Testing?
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477
Aug ’24
Task not executing at all
I have an 8th generation iPad, now updated with iPadOS 16.2 (20C65) and I have an issue that I also saw on earlier 16.* betas. Task is not executing at all. This is so frustrating because I have adopted async/await in my app, I support iOS 15+, everything was working fine but now that stuff inside Task { } is not executed my app seems to be broken. (Note: my main device is an iPhone 11, still on iOS 16.0, and it works fine there.) It is also frustrating to see no other developers are complaining about this, like it happens only with my app. I have debugged with print statements and breakpoints and I can say for sure that stuff is not executing. Does anybody have any ideas? Anything else I can try? FB11866066
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3.6k
Dec ’22
How to prevent screen recording from iOS 18 onwards as isCaptured is deprecated from iOS 18 ?
I am developing an iPhone app related to finance and currently I am using isCaptured value to prevent screen recording by checking the isCaptured value and if it is true then I blur the video recording. It was working fine while using UIScreen.main.isCaptured till iOS 17 . But for iOS 18 it became deprecated and it is not working any more. Below is the obj-c code block. - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions: (NSDictionary *)launchOptions { if (@available(iOS 11.0, *)) { BOOL isCaptured = [[UIScreen mainScreen] isCaptured]; if(isCaptured){ // Do the action for hiding the screen recording } } else{ // Fallback on earlier versions } return YES; } The replacement sceneCaptureState is working only for a scene-based app which uses UISceneDelegate lifecycle but it's not working for the old structure so now i have that problem, my iPhone app is very big and does not support scenes at all since we are following UIAppDelegate life cycle for years, what shall I do to prevent screen recording from iOS 18 onwards ? Note: My iPhone app does not support any scene configuration Please help me in this. Regards, Carol
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Aug ’24
UIAlertController new design on Mac OS Sonoma
The new alert on sonoma when you have 8 > actions its shows horizontal and goes out of the screen. Is there any way to bring back the old alert? let alert = UIAlertController(title: "Alert", message: "Message", preferredStyle: UIAlertController.Style.alert) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.destructive, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.default, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.default, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.destructive, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.default, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.default, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.destructive, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.default, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.default, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.default, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.destructive, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.default, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.default, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.destructive, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.default, handler: nil)) alert.addAction(UIAlertAction(title: "Click", style: UIAlertAction.Style.default, handler: nil)) self.present(alert, animated: true, completion: nil)
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1.1k
Oct ’23
NSKeyedUnarchiver.unarchivedObject(ofClass: , from: ) doesn't work with custom UIButton
My app creates dynamic copies of UI controls that are based on a custom UIButton subclass using this legacy approach: let archivedButton = try NSKeyedArchiver.archivedData(withRootObject: self, requiringSecureCoding: false) guard let buttonDuplicate = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(archivedButton) as? UIWagerButton else {return nil } I am currently trying to work passed the deprecation of NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data: Data) Per the guidance, I should be replacing that line with the following and ensuring that the custom class implements NSSecureCoding guard let buttonDuplicate = try NSKeyedUnarchiver.unarchivedObject(ofClass: UIWagerButton.self, from: archivedButton) else {return nil} However, while the code does compile and run, decoding the data reference throws the following error: value for key 'UIButtonStatefulContent' was of unexpected class 'NSMutableDictionary' I can only assume that if I get passed this specific property, there will be other properties that are also problematic. Question: Is this a bug? Or, am I now responsible for navigating the underlying property matrix of this UIControl to specifically, manually, handle the encoding and decoding of each of it's properties?
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409
Aug ’24