Hi,
I’m practicing with NavigationSplitView for macOS and customizing the sidebar. I’ve managed to adjust most parts, but I couldn’t remove the sidebar’s divider. It seems like it’s not possible in modern SwiftUI. My AppKit knowledge is also not very strong.
How can I remove the sidebar divider?
I want to use a plain background. I also solved it by creating my own sidebar, but I wanted to try it using NavigationSplitView.
Explore the various UI frameworks available for building app interfaces. Discuss the use cases for different frameworks, share best practices, and get help with specific framework-related questions.
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Is there a SwuiftUI way to remove the bezel from the compact DatePicker on MacOS?
I have an AppKit version but getting the font/background colors to behave is overly complicated for such a simple mission.
Hello.
I am currently building an app using AR Kit.
As for the UI, I am using SwiftUI and NavigationStack + NavigationLink for navigation and screen transitions!
Here I need to go back and forth between the AR screen and other screens.
If the number of screen transitions is small, this is not a problem.
However, if the number of screen transitions increases to 10 or 20, it crashes somewhere.
We are struggling with this problem. (The nature of the application requires multiple screen transitions.)
The crash log showed the following.
error: read memory from 0x1e387f2d4 failed
AR_Crash_Sample-2025-03-07-115914.txt
Incident Identifier: B23D806E-D578-4A95-8828-2A1E8D6BB7F8
Beta Identifier: 924A85AB-441C-41A7-9BC2-063940BDAF32
Hardware Model: iPhone16,1
Process: AR_Crash_Sample [2375]
Path: /private/var/containers/Bundle/Application/FAC3D662-DB10-434E-A006-79B9515D8B7A/AR_Crash_Sample.app/AR_Crash_Sample
Identifier: ar.crash.sample.AR.Crash.Sample
Version: 1.0 (1)
AppStoreTools: 16C7015
AppVariant: 1:iPhone16,1:18
Beta: YES
Code Type: ARM-64 (Native)
Role: Foreground
Parent Process: launchd [1]
Coalition: ar.crash.sample.AR.Crash.Sample [1464]
Date/Time: 2025-03-07 11:59:14.3691 +0900
Launch Time: 2025-03-07 11:57:47.3955 +0900
OS Version: iPhone OS 18.3.1 (22D72)
Release Type: User
Baseband Version: 2.40.05
Report Version: 104
Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Termination Reason: SIGNAL 6 Abort trap: 6
Terminating Process: AR_Crash_Sample [2375]
Triggered by Thread: 7
Application Specific Information:
abort() called
Thread 7 name: Dispatch queue: com.apple.arkit.depthtechnique
Thread 7 Crashed:
0 libsystem_kernel.dylib 0x1e387f2d4 __pthread_kill + 8
1 libsystem_pthread.dylib 0x21cedd59c pthread_kill + 268
2 libsystem_c.dylib 0x199f98b08 abort + 128
3 libc++abi.dylib 0x21ce035b8 abort_message + 132
4 libc++abi.dylib 0x21cdf1b90 demangling_terminate_handler() + 320
5 libobjc.A.dylib 0x18f6c72d4 _objc_terminate() + 172
6 libc++abi.dylib 0x21ce0287c std::__terminate(void (*)()) + 16
7 libc++abi.dylib 0x21ce02820 std::terminate() + 108
8 libdispatch.dylib 0x199edefbc _dispatch_client_callout + 40
9 libdispatch.dylib 0x199ee65cc _dispatch_lane_serial_drain + 768
10 libdispatch.dylib 0x199ee7158 _dispatch_lane_invoke + 432
11 libdispatch.dylib 0x199ee85c0 _dispatch_workloop_invoke + 1744
12 libdispatch.dylib 0x199ef238c _dispatch_root_queue_drain_deferred_wlh + 288
13 libdispatch.dylib 0x199ef1bd8 _dispatch_workloop_worker_thread + 540
14 libsystem_pthread.dylib 0x21ced8680 _pthread_wqthread + 288
15 libsystem_pthread.dylib 0x21ced6474 start_wqthread + 8
Perhaps I am using too much memory!
How can I address this phenomenon?
For the AR functionality, we are using UIViewRepresentable, which is written in UIKit and can be called from SwiftUI
import ARKit
import AsyncAlgorithms
import AVFoundation
import SCNLine
import SwiftUI
internal struct MeasureARViewContainer: UIViewRepresentable {
@Binding var tapCount: Int
@Binding var distance: Double?
@Binding var currentIndex: Int
var focusSquare: FocusSquare = FocusSquare()
let coachingOverlay: ARCoachingOverlayView = ARCoachingOverlayView()
func makeUIView(context: Context) -> ARSCNView {
let arView: ARSCNView = ARSCNView()
arView.delegate = context.coordinator
let configuration: ARWorldTrackingConfiguration = ARWorldTrackingConfiguration()
configuration.planeDetection = [.horizontal, .vertical]
if ARWorldTrackingConfiguration.supportsFrameSemantics(.sceneDepth) {
configuration.frameSemantics = [.sceneDepth, .smoothedSceneDepth]
}
arView.session.run(configuration, options: [.resetTracking, .removeExistingAnchors])
context.coordinator.sceneView = arView
context.coordinator.scanTarget()
coachingOverlay.session = arView.session
coachingOverlay.delegate = context.coordinator
coachingOverlay.goal = .horizontalPlane
coachingOverlay.activatesAutomatically = true
coachingOverlay.autoresizingMask = [.flexibleWidth, .flexibleHeight]
coachingOverlay.translatesAutoresizingMaskIntoConstraints = false
arView.addSubview(coachingOverlay)
return arView
}
func updateUIView(_ _: ARSCNView, context: Context) {
context.coordinator.mode = MeasurementMode(rawValue: currentIndex) ?? .width
if tapCount == 0 {
context.coordinator.resetMeasurement()
return
}
if distance != nil {
return
}
DispatchQueue.main.async {
if context.coordinator.distance == nil {
context.coordinator.handleTap()
}
}
}
static func dismantleUIView(_ uiView: ARSCNView, coordinator: Coordinator) {
uiView.session.pause()
coordinator.stopScanTarget()
coordinator.stopSpeech()
DispatchQueue.main.async {
uiView.removeFromSuperview()
}
}
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
class Coordinator: NSObject, ARSCNViewDelegate, ARSessionDelegate, ARCoachingOverlayViewDelegate {
var parent: MeasureARViewContainer
var sceneView: ARSCNView?
var startPosition: SCNVector3?
var pointedCount: Int = 0
var distance: Float?
var mode: MeasurementMode = .width
let synthesizer: AVSpeechSynthesizer = AVSpeechSynthesizer()
var scanTargetTask: Task<Void, Never>?
var currentResult: ARRaycastResult?
init(_ parent: MeasureARViewContainer) {
self.parent = parent
}
// ... etc
}
}
I have a SwiftUI View I've introduced to a UIKit app, using UIHostingController. The UIView instance that contains the SwiftUI view is animated using auto layout constraints. In this code block, when a view controller's viewDidAppear method I'm creating the hosting controller and adding its view as a subview of this view controller's view, in addition to doing the Container View Controller dance.
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let hostingViewController = UIHostingController(rootView: TestView())
hostingViewController.view.translatesAutoresizingMaskIntoConstraints = false
addChild(hostingViewController)
view.addSubview(hostingViewController.view)
let centerXConstraint = hostingViewController.view.centerXAnchor.constraint(equalTo: view.centerXAnchor)
let topConstraint = hostingViewController.view.topAnchor.constraint(equalTo: view.topAnchor)
widthConstraint = hostingViewController.view.widthAnchor.constraint(equalToConstant: 361)
heightConstraint = hostingViewController.view.heightAnchor.constraint(equalToConstant: 342)
NSLayoutConstraint.activate([centerXConstraint, topConstraint, widthConstraint, heightConstraint])
hostingViewController.didMove(toParent: self)
self.hostingViewController = hostingViewController
}
I add a button to the UI which will scale the UIHostingViewController by adjusting its height and width constraints. When it's tapped, this action method runs.
@IBAction func animate(_ sender: Any) {
widthConstraint.constant = 120.3
heightConstraint.constant = 114.0
UIView.animate(withDuration: 0.5) {
self.view.layoutIfNeeded()
}
}
The problem is, the SwiftUI view's contents "jump" at the start of the animation to the final height, then animate into place. I see this both using UIView.animate the UIKit way, or creating a SwiftUI animation and calling `UIView.
What else do I need to add to make this animate smoothly?
Hello,
My goal is to have a NavigationStack whose root view is determined based on its height and width. To do so, I'm using ViewThatFits, which should choose the right view to display. It is working fine, but unexpectedly both views trigger onAppear, whereas only the appropriate one should. This causes the logic in both closures to be executed, which is not intended.
The code below demonstrates the problem:
struct NavigationStackContentView: View {
var body: some View {
NavigationStack {
ViewThatFits(in: .vertical) {
Color.yellow
.onAppear { print("|-> on appear: yellow") }
.onDisappear { print("|-> on disappear: yellow") }
Color.red
.frame(width: 1500, height: 1500)
.onAppear { print("|-> on appear: red") }
.onDisappear { print("|-> on disappear: red") }
}
}
}
}
this produces:
|-> on appear: red
|-> on disappear: red
|-> on appear: yellow
When ViewThatFits is not nested within NavigationStack, the problem does not occur — only the yellow view (in this sample) triggers onAppear, which is the expected behavior. I also checked the macOS version, and the problem does not occur at all, whether within NavigationStack or not.
This example is simple and demonstrates that the larger view is the second one. When I switch their places, the problem does not occur because it recognizes that the first view would not fit at this point. However, in my case I will have these views without knowing which one will not fit, so switching their order is not a viable solution if this works without NavigationStack.
Am I doing something wrong, or is this a bug?
//
iOS: 18.3.1
Xcode: 16.2
TLDR: What rules ensure you won't have sporadic run-time crashes when using ViewThatFits?
My app crashes - luckily reproducible. But the code appeared syntacticly and logically correct.
Simplified excerpt:
https://github.com/alanrick/Experiment3
The crash is caused by ViewThatFits being overwhelmed by concurrent changes in other views, exacerbated by animation effects. In the original code the problem was even worse because I'd gone overboard and used ViewThatFits in sub-views making the whole thing too dynamic.
My first rule is:
Do not use nested ViewThatFits.
But this alone is not sufficient. What other rules can I apply to ensure I won't have hard-to-detect run-time crashes when using ViewThatFits?
Topic:
UI Frameworks
SubTopic:
SwiftUI
Is it the default behavior that the standard back swipe (interactivePopGestureRecognizer) does not work when running a designed for iPhone app on an iPad?
To my knowledge, all apps behave this way.
Are there any workarounds?
I'm making a custom control, specifically a checkbox next to a "label." I want the label parameter, like many in Apple's built-in controls, to take a view-building closure.
But I can't figure out the correct syntax. I looked at the declaration of Apple's NavigationLink control for clues:
public struct NavigationLink<Label, Destination> : View where Label : View, Destination : View {
/// Creates a navigation link that presents the destination view.
/// - Parameters:
/// - destination: A view for the navigation link to present.
/// - label: A view builder to produce a label describing the `destination`
/// to present.
public init(@ViewBuilder destination: () -> Destination, @ViewBuilder label: () -> Label)
But when I mimic this, the compiler complains about the body() function:
struct CheckboxItem<Label> : View where Label : View
{
let stateCheck: () -> Bool
let label: () -> any View
let boxSize: CGFloat
init(withStateCheck: @escaping () -> Bool, boxSize: CGFloat, @ViewBuilder label: @escaping () -> Label)
{
stateCheck = withStateCheck
self.label = label
self.boxSize = boxSize
}
var body: some View
{
HStack
{ <-- ERROR: "Type 'any View' cannot conform to 'View'"
Image(systemName: stateCheck() ? "checkmark.square" : "square")
.resizable()
.aspectRatio(contentMode: .fit)
.frame(width: boxSize, height: boxSize)
.foregroundColor(AppStyle.labelColor)
.opacity(0.75)
label()
}
}
}
Also, note that I had to put @escaping before my label parameter, but that's not seen in Apple's.
Any ideas?
Topic:
UI Frameworks
SubTopic:
SwiftUI
This is a very strange behavior when pushing vc that I have never seen since I started coding. The pushed ViewController is transparent and only navBarTitle is shown. After the push, you can't control anything unless you go back to the home screen.
STEPS TO REPRODUCE
Long press currency change button below.(currencyWrapper)
Call selectCountry and this bug happens.
SourceCode
let currencyWrapper = UIView()
private func configureCurrencyCard(){
//The strange behavior shows up after long pressing this
currencyWrapper.backgroundColor = .white
currencyWrapper.addTarget(self, action: #selector(changeCurrency))
currencyWrapper.setWidth(currencyChangeIcon.follow(by: 16, x: true))
currencyWrapper.setCenterX(w1/2)
currencyWrapper.setHeight(currencyLabel.follow(by: 12, x: false))
currencyWrapper.roundToCircle(true)
view.addSubview(currencyWrapper)
}
private func selectCountry(country: Country){
let vc = CountryViewController(country: country)
vc.hidesBottomBarWhenPushed = true
navigationController?.pushViewController(vc, animated: true)
}
import SwiftUI
struct Product: Identifiable {
let id = UUID()
let name: String
let pricePerKg: Double
}
struct ContentView: View {
@State private var selectedProduct: Product?
@State private var quantity: Double = 1.0
@State private var orderDate = Date()
@State private var showingConfirmation = false
let products = [
Product(name: "Lamb", pricePerKg: 15.0),
Product(name: "Beef", pricePerKg: 20.0),
Product(name: "Chicken", pricePerKg: 10.0)
]
var body: some View {
NavigationView {
Form {
Section(header: Text("Select Meat")) {
Picker("Meat Type", selection: $selectedProduct) {
ForEach(products) { product in
Text(product.name).tag(product as Product?)
}
}
}
if let selectedProduct = selectedProduct {
Section(header: Text("Quantity (kg)")) {
Stepper(value: $quantity, in: 0.5...10, step: 0.5) {
Text("\(quantity, specifier: "%.1f") kg")
}
}
Section(header: Text("Delivery Date")) {
DatePicker("Select Date", selection: $orderDate, in: Date()..., displayedComponents: .date)
}
Section(header: Text("Total Price")) {
Text("$\(selectedProduct.pricePerKg * quantity, specifier: "%.2f")")
}
Button("Confirm Order") {
showingConfirmation = true
}
.alert(isPresented: $showingConfirmation) {
Alert(title: Text("Order Confirmed"), message: Text("You have ordered \(quantity, specifier: "%.1f") kg of \(selectedProduct.name) for \(orderDate.formatted(date: .long, time: .omitted))."), dismissButton: .default(Text("OK")))
}
}
}
.navigationTitle("Halal Butcher")
}
}
}
@main
struct HalalButcherApp: App {
var body: some Scene {
WindowGroup {
ContentView()
}
}
}
I have a scrollview displaying a sequence of circles, which a user should be able to scroll through to select an item. When the user stops scrolling and the animation comes to rest the circle selected should display screen-centered.
I had hoped to achieve this using .scrollPosition(id: selectedItem, anchor: .center) but it appears that the anchor argument is ignored when scrolled manually. (BTW - I searched but didn't locate this aspect in the Apple documentation so I'm not confident that this observation is really correct).
https://youtu.be/TpXDTuL5yPQ
The video shows the user-scrolling behaviour, and also the snap-to-anchor that I would like to achieve, but I would like this WITHOUT forcing a button press.
I could juggle the container size and size of the circles so that they naturally fit centered into the screen, but I would prefer a more elegant solution.
How can I force the scrolling to come to rest such that the circle glides to rest in the center of the screen/container?
struct ItemChooser: View {
@State var selectedItem: Int?
var body: some View {
VStack {
Text("You have picked: \(selectedItem ?? 0)")
ScrollHorizontalItemChooser(selectedItem: $selectedItem)
}
}
}
#Preview {
ItemChooser(selectedItem: 1)
}
struct ScrollHorizontalItemChooser: View {
@Binding var selectedItem: Int?
@State var scrollAlignment: UnitPoint? = .center
let ballSize: CGFloat = 150
let items = Array(1...6)
@State var scrollPosition: ScrollPosition = ScrollPosition()
var body: some View {
VStack {
squareUpButton
ScrollView(.horizontal) {
HStack(spacing: 10) {
showBalls
}
.scrollTargetLayout()
}
.scrollPosition(id: $selectedItem, anchor: scrollAlignment )
.overlay{ crosshairs } }
}
var crosshairs: some View {
Image(systemName: "scope").scaleEffect(3.0).opacity(0.3)
}
@ViewBuilder
var showBalls: some View {
let screenWidth: CGFloat = UIScreen.main.bounds.width
var emptySpace: CGFloat {screenWidth / 2 - ballSize / 2 - 10}
Spacer(minLength: emptySpace)
ForEach(items, id: \.self) { item in
poolBall( item)
.id(item)
}
Spacer(minLength: emptySpace)
}
@ViewBuilder
private func poolBall(_ item: Int) -> some View {
Text("Item \(item)")
.background {
Circle()
.foregroundColor(Color.green)
.frame(width: ballSize, height: ballSize)
}
.frame(width: ballSize, height: ballSize)
}
@ViewBuilder
var squareUpButton: some View {
var tempSelected: Int? = nil
Button("Square up with Anchor") {
tempSelected = selectedItem
selectedItem = 0
DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
selectedItem = tempSelected ?? 0
}
}
}
}
Topic:
UI Frameworks
SubTopic:
SwiftUI
I've encountered an issue where storing a throws(PermissionError) closure as a property inside a SwiftUI View causes a runtime crash on iOS 17, while it works correctly on iOS 18.
Here’s an example of the affected code:
enum PermissionError: Error {
case denied
}
struct PermissionCheckedView<AllowedContent: View, DeniedContent: View>: View {
var protectedView: () throws(PermissionError) -> AllowedContent
var deniedView: (PermissionError) -> DeniedContent
init(
@ViewBuilder protectedView: @escaping () throws(PermissionError) -> AllowedContent,
@ViewBuilder deniedView: @escaping (PermissionError) -> DeniedContent
) {
self.protectedView = protectedView
self.deniedView = deniedView
}
public var body: some View {
switch Result(catching: protectedView) {
case .success(let content): content
case .failure(let error): deniedView(error)
}
}
}
@main
struct TestApp: App {
var body: some Scene {
WindowGroup {
PermissionCheckedView {
} deniedView: { _ in
}
}
}
}
Specifically this is the stack trace (sorry for the picture I didn't know how to get the txt):
If I use var protectedView: () throws -> AllowedContent without typed throws it works.
When I present a view controller, whose view is a SwiftUI View, via presentAsModalWindow(_:) the presented window is no longer centered horizontally to the screen, but rather its origin is there. I know this issue occurs for macOS 15.2+, but can't tell if it is from 15.0+. I couldn't find any documentation on why was this changed.
Here's an example code that represents my architecture:
class RootViewController: NSViewController {
private lazy var button: NSButton = NSButton(
title: "Present",
target: self,
action: #selector(presentView))
override func viewDidLoad() {
super.viewDidLoad()
// Add button to tree
}
@objc func presentView() {
presentAsModalWindow(PresentedViewController())
}
}
class PresentedViewController: NSViewController {
override loadView() {
view = NSHostingView(rootView: MyView())
}
}
struct MyView: View {
/* impl */
}
I tried to create a Text View using attributedString. I want to set the line height using paragraphStyle and return the Text, but paragraphStyle is not being applied. Why is that?
extension Text {
init?(_ content: String, font: StyleType, color: Color = .ppBlack) {
var attributedString = AttributedString(content)
attributedString.font = Font.custom(font.fontWeight, fixedSize: font.fontSize)
attributedString.foregroundColor = color
let paragraphStyle = NSMutableParagraphStyle()
paragraphStyle.minimumLineHeight = 16
paragraphStyle.maximumLineHeight = 16
paragraphStyle.lineSpacing = 0
attributedString.mergeAttributes(.init([.paragraphStyle: paragraphStyle]))
self = Text(attributedString)
}
}
I have a NSViewController as the root view and have a switui view embedded in it via NSHostingView.
override func loadView() {
self.view = NSHostingView(rootView: SwiftUiView())
}
}
In the SwiftUiView, I have a TextField and an NSTextView embedded using NSViewRepresentable, along with a few buttons. There is also a menu:
Menu {
ForEach(menuItems), id: \.self) { item in
Button {
buttonClicked()
} label: {
Text(item)
}
}
} label: {
Image("DropDown")
.contentShape(Rectangle())
.frame(maxWidth: .infinity)
.frame(maxHeight: .infinity)
}
The NSTextView and TextField work fine, and I can type in them until I click on the menu or show an alert. After that, I can no longer place my cursor in the text fields. I am able to select the text but not type in it. When I click on the NSTextView or TextField, nothing happens.
At first, I thought it was just a cursor visibility issue and tried typing, but I received an alert sound. I've been trying to fix this for a couple of days and haven't found any related posts. Any help would be greatly appreciated.
I work on an iOS app using SwiftUI and SwiftData. I added a computed property to one of my models - Parent - that uses relationship - array of Child models - data and I started getting strange problems. Let me start with models:
@Model
final class Parent {
var name: String
@Relationship(deleteRule: .cascade, inverse: \Child.parent)
var children: [Child]? = []
var streak: Int {
// Yes, I know that's not optimal solution for such counter ;)
guard let children = children?.sorted(using: SortDescriptor(\.date, order: .reverse)) else { return 0 }
var date = Date.now
let calendar = Calendar.current
for (index, child) in children.enumerated() {
if !calendar.isDate(child.date, inSameDayAs: date) {
return index
}
date = calendar.date(byAdding: .day, value: -1, to: date) ?? .now
}
return children.count
}
init(name: String) {
self.name = name
}
}
@Model
final class Child {
var date: Date
@Relationship(deleteRule: .nullify)
var parent: Parent?
init(date: Date, parent: Parent) {
self.date = date
self.parent = parent
}
}
At first everything works as expected. The problem arises once I try to remove one of child from the parent instance. I remove the value from context and save changes without any problems, at least not ones that can be caught by do { } catch. But instead of refreshing UI I get an signal SIGABRT somewhere inside SwiftData internals that points to the line where I'm trying (inside View body) get a child from a Query:
struct LastSevenDaysButtons: View {
@Environment(\.modelContext)
private var modelContext
@Query
private var children: [Child]
private let dates: [Date]
private let parent: Parent
init(for parent: Parent) {
self.parent = parent
var lastSevenDays = [Date]()
let calendar = Calendar.current
let firstDate = calendar.date(byAdding: .day, value: -6, to: calendar.startOfDay(for: .now)) ?? .now
var date = firstDate
while date <= .now {
lastSevenDays.append(date)
date = calendar.date(byAdding: .day, value: 1, to: date) ?? .now
}
dates = lastSevenDays
let parentId = parent.persistentModelID
_children = Query(
filter: #Predicate {
$0.parent?.persistentModelID == parentId && $0.date >= firstDate
},
sort: [SortDescriptor(\Child.date, order: .reverse)],
animation: .default
)
}
var body: some View {
VStack {
HStack(alignment: .top) {
ForEach(dates, id: \.self) { date in
// Here is the last point on stack from my code that I see
let child = children.first { $0.date == date }
Button {
if let child {
modelContext.delete(child)
} else {
modelContext.insert(Child(date: date, parent: parent))
}
do {
try modelContext.save()
} catch {
print("Can't save changes for \(parent.name) on \(date.formatted(date: .abbreviated, time: .omitted)): \(error.localizedDescription)")
}
} label: {
Text("\(date.formatted(date: .abbreviated, time: .omitted))")
.foregroundStyle(child == nil ? .red : .blue)
}
}
}
}
}
}
The LastSevenDaysButtons View is kind of deep in a View hierarchy:
RootView -> ParentList -> ParentListItem -> LastSevenDaysButtons
However once I move insides of ParentList to RootView application works just fine, although I see and warning: === AttributeGraph: cycle detected through attribute 6912 ===.
What could be that I do wrong in here? I believe it must something I'm missing here, but after 2 days of debug, trial and errors, I can't think clearly anymore.
Here is the minimal repro I managed to create: Signal SIGABRT on accessing values from SwiftData query
I'm trying to create a form which reads and writes data to a dictionary. when I type something in a field whole form seems to update. Is there anyway to only update the field I'm typing? Android compose have something called SnapshotStateMap which allows smart re-rendering.
Topic:
UI Frameworks
SubTopic:
SwiftUI
Hello!
I’m experiencing a crash in my iOS/iPadOS app related to a CALayer rendering process. The crash occurs when attempting to render a UIImage on a background thread. The crashes are occurring in our production app, and while we can monitor them through Crashlytics, we are unable to reproduce the issue in our development environment.
Relevant Code
I have a custom view controller that handles rendering CALayers onto images. This method creates a CALayer on the main thread and then starts a detached task to render this CALayer into a UIImage. The whole idea is learnt from this StackOverflow post: https://stackoverflow.com/a/77834613/9202699
Here are key parts of my implementation:
class MyViewController: UIViewController {
@MainActor
func renderToUIImage(size: CGSize, itemsToDraw: [MyDrawingItem], transform: CGAffineTransform) async -> UIImage? {
// Create CALayer and add it to the view.
CATransaction.begin()
let customLayer = MyDrawingLayer()
customLayer.setupContent(itemsToDraw: itemsToDraw)
// Position the frame off-screen to it hidden.
customLayer.frame = CGRect(
origin: CGPoint(x: -100 - size.width, y: -100 - size.height),
size: size)
customLayer.masksToBounds = true
customLayer.drawsAsynchronously = true
view.layer.addSublayer(customLayer)
CATransaction.commit()
// Render CALayer to UIImage in background thread.
let image = await Task.detached {
customLayer.setNeedsDisplay()
let renderer = UIGraphicsImageRenderer(size: size)
let image = renderer.image { // CRASH happens on this line
let cgContext = $0.cgContext
cgContext.saveGState()
cgContext.concatenate(transform)
customLayer.render(in: cgContext)
cgContext.restoreGState()
}
return image
}.value
// Remove the CALayer from the view.
CATransaction.begin()
customLayer.removeFromSuperlayer()
CATransaction.commit()
return image
}
}
class MyDrawingLayer: CALayer {
var itemsToDraw: [MyDrawingItem] = []
func setupContent(itemsToDraw: [MyDrawingItem]) {
self.itemsToDraw = itemsToDraw
}
override func draw(in ctx: CGContext) {
for item in itemsToDraw {
// Render the item to the context (example pseudo-code).
// All items are thread-safe to use.
// Things to draw may include CGPath, CGImages, UIImages, NSAttributedString, etc.
item.draw(in: ctx)
}
}
}
Crash Log
The crash occurs at the following location:
Crashed: com.apple.root.default-qos.cooperative
0 MyApp 0x5cb300 closure #1 in closure #1 in MyViewController.renderToUIImage(size: CGSize, itemsToDraw: [MyDrawingItem], transform: CGAffineTransform) + 4313002752 (<compiler-generated>:4313002752)
1 MyApp 0x5cb300 closure #1 in closure #1 in MyViewController.renderToUIImage(size: CGSize, itemsToDraw: [MyDrawingItem], transform: CGAffineTransform) + 4313002752 (<compiler-generated>:4313002752)
2 MyApp 0x1a4578 AnyModifier.modified(for:) + 4308649336 (<compiler-generated>:4308649336)
3 MyApp 0x7b4e64 thunk for @escaping @callee_guaranteed (@guaranteed UIGraphicsPDFRendererContext) -> () + 4315008612 (<compiler-generated>:4315008612)
4 UIKitCore 0x1489c0 -[UIGraphicsRenderer runDrawingActions:completionActions:format:error:] + 324
5 UIKitCore 0x14884c -[UIGraphicsRenderer runDrawingActions:completionActions:error:] + 92
6 UIKitCore 0x148778 -[UIGraphicsImageRenderer imageWithActions:] + 184
7 MyApp 0x5cb1c0 closure #1 in MyViewController.renderToUIImage(size: CGSize, itemsToDraw: [MyDrawingItem], transform: CGAffineTransform) + 100 (FileName.swift:100)
8 libswift_Concurrency.dylib 0x60f5c swift::runJobInEstablishedExecutorContext(swift::Job*) + 252
9 libswift_Concurrency.dylib 0x62514 swift_job_runImpl(swift::Job*, swift::SerialExecutorRef) + 144
10 libdispatch.dylib 0x15ec0 _dispatch_root_queue_drain + 392
11 libdispatch.dylib 0x166c4 _dispatch_worker_thread2 + 156
12 libsystem_pthread.dylib 0x3644 _pthread_wqthread + 228
13 libsystem_pthread.dylib 0x1474 start_wqthread + 8
Questions
Is it safe to run UIGraphicsImageRenderer.image on the background thread?
Given that I want to leverage GPU rendering, what are some best practices for rendering images off the main thread while ensuring stability?
Are there alternatives to using UIGraphicsImageRenderer for background rendering that can still take advantage of GPU rendering?
It is particularly interesting that the crash logs indicate the error may be related to UIGraphicsPDFRendererContext (crash log line number 3). It would be very helpful if someone could explain the connection between starting and drawing on a UIGraphicsImageRenderer and UIGraphicsPDFRendererContext.
Any insights or guidance on this issue would be greatly appreciated. Thanks!!!
I would like to report a memory leak issue in watchOS 11.2 that occurs when using .navigationTitle() inside a sheet. This behavior is reproducible both on the simulator and on a real device, but not on iOS. While this does not register as a leak in Instruments, the deinit of the DetailsViewModel is never called, and multiple instances of the view model accumulate in the Memory Graph Debugger. Commenting out .navigationTitle("Sheet View") resolves the issue, and deinit prints as expected. Using @MainActor on the DetailsViewModel does not fix the issue. Nor does switching to @StateObject and using ObservableObject resolve the memory retention.
This issue seems related to other SwiftUI memory leaks that have been reported:
https://developer.apple.com/forums/thread/738840
https://developer.apple.com/forums/thread/736110?login=true&page=1#769898022
https://developer.apple.com/forums/thread/737967?answerId=767599022#767599022
Feedback Number: FB16442048
struct MainView: View {
var body: some View {
NavigationStack {
NavigationLink("Details", value: 1)
.navigationDestination(for: Int.self) { _ in
DetailsView()
}
}
}
}
struct SheetObject: Identifiable {
let id = UUID()
let date: Date
let value: Int
}
@Observable
@MainActor
final class DetailsViewModel {
var sheetObject: SheetObject?
init() {
print("Init")
}
deinit {
print("Deinit")
}
func onAppear() async {
try? await Task.sleep(for: .seconds(2))
sheetObject = .init(date: .now, value: 1)
}
}
struct DetailsView: View {
@State private var viewModel = DetailsViewModel()
@Environment(\.dismiss) var dismiss
var body: some View {
Text("Detail View. Going to sheet, please wait...")
.task {
await viewModel.onAppear()
}
.sheet(item: $viewModel.sheetObject) { sheetObject in
SheetView(sheetObject: sheetObject)
.onDisappear {
dismiss()
}
}
}
}
struct SheetView: View {
let sheetObject: SheetObject
@Environment(\.dismiss) var dismiss
var body: some View {
NavigationStack {
VStack {
Text(sheetObject.date.formatted())
Text(sheetObject.value.formatted())
Button("Dismiss") {
dismiss()
}
}
.navigationTitle("Sheet View") // This line causes a memory leak. Commenting out, you will see "Deinit" be printed.
}
}
}
Topic:
UI Frameworks
SubTopic:
SwiftUI
I've been running into an issue using .fileImporter in SwiftUI already for a year. On iPhone simulator, Mac Catalyst and real iPad it works as expected, but when it comes to the test on a real iPhone, the picker just won't let you select files. It's not the permission issue, the sheet won't close at all and the callback isn't called. At the same time, if you use UIKits DocumentPickerViewController, everything starts working as expected, on Mac Catalyst/Simulator/iPad as well as on a real iPhone.
Steps to reproduce:
Create a new Xcode project using SwiftUI.
Paste following code:
import SwiftUI
struct ContentView: View {
@State var sShowing = false
@State var uShowing = false
@State var showAlert = false
@State var alertText = ""
var body: some View {
VStack {
VStack {
Button("Test SWIFTUI") {
sShowing = true
}
}
.fileImporter(isPresented: $sShowing, allowedContentTypes: [.item]) {result in
alertText = String(describing: result)
showAlert = true
}
VStack {
Button("Test UIKIT") {
uShowing = true
}
}
.sheet(isPresented: $uShowing) {
DocumentPicker(contentTypes: [.item]) {url in
alertText = String(describing: url)
showAlert = true
}
}
.padding(.top, 50)
}
.padding()
.alert(isPresented: $showAlert) {
Alert(title: Text("Result"), message: Text(alertText))
}
}
}
DocumentPicker.swift:
import SwiftUI
import UniformTypeIdentifiers
struct DocumentPicker: UIViewControllerRepresentable {
let contentTypes: [UTType]
let onPicked: (URL) -> Void
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
func makeUIViewController(context: Context) -> UIDocumentPickerViewController {
let documentPicker = UIDocumentPickerViewController(forOpeningContentTypes: contentTypes, asCopy: true)
documentPicker.delegate = context.coordinator
documentPicker.modalPresentationStyle = .formSheet
return documentPicker
}
func updateUIViewController(_ uiViewController: UIDocumentPickerViewController, context: Context) {}
class Coordinator: NSObject, UIDocumentPickerDelegate {
var parent: DocumentPicker
init(_ parent: DocumentPicker) {
self.parent = parent
}
func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
print("Success!", urls)
guard let url = urls.first else { return }
parent.onPicked(url)
}
func documentPickerWasCancelled(_ controller: UIDocumentPickerViewController) {
print("Picker was cancelled")
}
}
}
Run the project on Mac Catalyst to confirm it working.
Try it out on a real iPhone.
For some reason, I can't attach a video, so I can only show a screenshot