I've encountered a major issue with the iOS 18.1 RC and watchOS 11.1 RC. It appears that complications running on WidgetKit cannot be synced as .watchface to these new release candidates. The error message indicates that "the Watch Faces app and complication are not available," which is affecting all apps utilizing WidgetKit. This issue renders all WidgetKit-based complications unusable on watchOS 11.1 RC. It’s a serious problem for those of us who rely on these complications for our apps and for users expecting consistent functionality. APPLE, PLEASE FIX THIS ISSUE ASAP! This bug is a significant setback for developers and users alike, and any guidance or updates would be greatly appreciated.

I'm trying to make a Swift Chart where 24 AreaMarks an hour apart on X axis over a day display a vertical gradient. The gradient is vertical and is essentially [Color.opacity(0.1),Colour,Color.opacity(0.1] The idea here is where the upper and lower points of each AreaMark are the same or close to each other in the Y axis, the chart essentially displays a line, where they are far apart you get a nice fading vertical gradient. However, it seems that the .alignsMarkStylesWithPlotArea modifier is always set for AreaMarks even if manually applying it false. Investigating further, I've learnt that with AreaMarks in a series, Swift Charts seems to only listen to the first foreground style set in. I've created some sample code to demonstrate this. struct DemoChartView: View { var body: some View { Chart { AreaMark(x: .value("Time", Date().addingTimeInterval(0)), yStart: .value("1", 40), yEnd: .value("2", 60)) .foregroundStyle(LinearGradient(colors: [.pink, .teal], startPoint: .top, endPoint: .bottom)) .alignsMarkStylesWithPlotArea(false) AreaMark(x: .value("Time", Date().addingTimeInterval(3600)), yStart: .value("1", 44), yEnd: .value("2", 58)) .foregroundStyle(LinearGradient(colors: [.orange, .yellow], startPoint: .top, endPoint: .bottom)) .alignsMarkStylesWithPlotArea(false) AreaMark(x: .value("Time", Date().addingTimeInterval(03600*2)), yStart: .value("1", 50), yEnd: .value("2", 90)) .foregroundStyle(LinearGradient(colors: [.green, .blue], startPoint: .top, endPoint: .bottom)) .alignsMarkStylesWithPlotArea(false) } } } Which produces this: So here, all the different .foregroundStyle LinearGradients are being ignored AND the .alignsMarkStylesWithPlotArea(false) is also ignored - the amount of pink on the first mark is different to the second and third 🤷‍♂️ Has anyone encountered this. Are AreaMarks the correct choice or are they just not setup to create this type of data display. Thanks

I'm adding widget interactivity to my home screen widgets via buttons and AppIntents, but running into some interesting behavior the way the timeline is reloaded after. I'm following this guide from Apple https://developer.apple.com/documentation/widgetkit/adding-interactivity-to-widgets-and-live-activities And the widget is guaranteed to be reloaded when a button pressed with an intent, But whenever the AppIntent is done with the perform action, the widget timeline is always reloaded twice. It's also interesting to note that both reloads happen after the perform method. If you add a 10 second sleep in the perform, nothing happens for 10 seconds, then both reloads happen. This issue with this is 2-fold. calculating and rendering the entire widget timeline can be Networking and DB intensive operations, so I would ideally like to avoid doing all the work twice and save the users battery and processing. The even worse issue, sometimes data on the server changes in between the split second duplicate widget timeline reloads, causing the widget to flash one state, then update to another a second later which is not a good user experience. I have a sample project which shows the issue and is very easy to reproduce. The widget simply keeps track of the number of reloads. To reproduce: Add the widget to the homescreen Press the refresh button, and observe the timeline refresh count always goes up by 2. I've filed a Feedback and attached the sample project and screen recording for anyone to reproduce. FB15595835

Before I waste time creating an Apple Developer Support ticket, I’m hoping an Apple DTS engineer can confirm if this is just log noise. Here’s the code: import SwiftUI struct ContentView: View { @State private var editMode: EditMode = .inactive @State private var items = ["Item 1", "Item 2", "Item 3"] var body: some View { NavigationStack { List { ForEach(items, id: \.self) { item in Text(item) } .onDelete { indexSet in items.remove(atOffsets: indexSet) } } .environment(\.editMode, $editMode) .toolbar { ToolbarItem(placement: .topBarTrailing) { EditButton() .environment(\.editMode, $editMode) } } } } } #Preview { ContentView() } When you run this code and tap Edit, you’ll initially get: CoreSVG has logged an error. Set environment variabe [sic] "CORESVG_VERBOSE" to learn more. After setting CORESVG_VERBOSE = YES, you’ll see: CoreSVG: Error: NULL ref passed to getObjectCoreSVG: Error: NULL ref passed to getObject This error only appears the first time Edit is tapped after a build and run. It won't happen again, even after force-quitting and reopening the app. The issue also only happens on iOS 18.0 and 18.1—I can’t reproduce it on iOS 17.5. Fortunately, it doesn’t seem to cause any negative side effects. Is this just log noise?

Hi, I have noticed a major uptick in crash reports, ever since I updated my app for macOS Sequoia. All of them have to do with NSOutlineView, and they all have a similar internal API in the crash log, which shows that the issue is something to do with the framework. They all have references to NSConcreteMapTable and _TtCs12_SwiftObject isEqual. The issue isn't reproducible, but it's reported by many different users, all on macOS15+, and it was never an issue with macOS14 or below, so I'm not sure what to do about it. Here's a couple of examples of the new crash reports: Date/Time: 2024-10-29T06:55:19.999Z Launch Time: 2024-10-29T06:50:08Z OS Version: Mac OS X 15.0.1 (24A348) Report Version: 104 Exception Type: SIGTRAP Exception Codes: TRAP_BRKPT at 0x1a98c9c90 Crashed Thread: 0 Thread 0 Crashed: 0 libswiftCore.dylib 0x00000001a98c9c90 -[_TtCs12_SwiftObject isEqual:] + 240 1 Foundation 0x0000000199ad4e0c probeGC + 408 2 Foundation 0x0000000199b01e6c -[NSConcreteMapTable removeObjectForKey:] + 76 3 AppKit 0x000000019c5966a8 _NSOVFreeRowEntry + 44 4 AppKit 0x000000019c5965c4 _NSOVRecursiveFreeChildrenAndItem + 100 5 AppKit 0x000000019c59649c _NSOVFastRemoveChildRowEntries + 260 6 AppKit 0x000000019c595d40 -[NSOutlineView reloadItem:reloadChildren:] + 1016 7 MyApp 0x0000000104b454fc CJ_CRM.MacCJSidebarViewController.compareContactsDictionariesForPublicGroups() -> () (MacCJSidebarViewController.swift:1611) 8 MyApp 0x0000000104b44518 $s20MyApp26MacCJSidebarViewControllerC27contactsChangedNotificationyySo14NSNotificationCFySo7NSTimerCYbcfU_ (MacCJSidebarViewController.swift:461) 9 MyApp 0x0000000104ba5310 $sSo7NSTimerCIeghg_ABIeyBhy_TR (<compiler-generated>:0) 10 Foundation 0x0000000199b64cfc __NSFireTimer + 100 11 CoreFoundation 0x0000000198988184 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 28 12 CoreFoundation 0x0000000198987e28 __CFRunLoopDoTimer + 1008 13 CoreFoundation 0x0000000198987938 __CFRunLoopDoTimers + 352 14 CoreFoundation 0x000000019896d0f0 __CFRunLoopRun + 1852 15 CoreFoundation 0x000000019896c334 CFRunLoopRunSpecific + 568 16 HIToolbox 0x00000001a3da50cc RunCurrentEventLoopInMode + 288 17 HIToolbox 0x00000001a3daaebc ReceiveNextEventCommon + 632 18 HIToolbox 0x00000001a3dab020 _BlockUntilNextEventMatchingListInModeWithFilter + 72 19 AppKit 0x000000019c4b0a70 _DPSNextEvent + 656 20 AppKit 0x000000019cdd67b8 -[NSApplication(NSEventRouting) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 684 21 AppKit 0x000000019c4a3b7c -[NSApplication run] + 476 22 AppKit 0x000000019c47a44c NSApplicationMain + 884 23 MyApp 0x0000000104a1e26c main (main.m:24) 24 ??? 0x0000000198504274 0x0 + 0 Another one with a different trigger but same internal API: Date/Time: 2024-10-29T16:49:12.999Z Launch Time: 2024-10-29T15:51:27Z OS Version: Mac OS X 15.1 (24B83) Report Version: 104 Exception Type: SIGSEGV Exception Codes: SEGV_MAPERR at 0x4cde11282080 Crashed Thread: 0 Thread 0 Crashed: 0 libswiftCore.dylib 0x00000001a04efa1c isSubclass(swift::TargetMetadata<swift::InProcess> const*, swift::TargetMetadata<swift::InProcess> const*) + 28 1 libswiftCore.dylib 0x00000001a04ef9f8 _swift_class_isSubclass + 12 2 libswiftCore.dylib 0x00000001a04ffa9c -[_TtCs12_SwiftObject isEqual:] + 252 3 Foundation 0x00000001906b4cec probeGC + 408 4 Foundation 0x00000001906b4adc -[NSConcreteMapTable objectForKey:] + 64 5 AppKit 0x00000001930f8eec -[NSOutlineView _rowEntryForItem:requiredRowEntryLoadMask:] + 48 6 AppKit 0x00000001930f8e80 -[NSOutlineView parentForItem:] + 24 7 MyApp 0x0000000100e2faec MyApp.MacCJSidebarViewController.outlineView(_: __C.NSOutlineView, selectionIndexesForProposedSelection: Foundation.IndexSet) -> Foundation.IndexSet (MacCJSidebarViewController.swift:759) 8 MyApp 0x0000000100e30dbc @objc MyApp.MacCJSidebarViewController.outlineView(_: __C.NSOutlineView, selectionIndexesForProposedSelection: Foundation.IndexSet) -> Foundation.IndexSet (<compiler-generated>:0) 9 AppKit 0x000000019324c4e4 -[NSTableView _userSelectableRowIndexesForProposedSelection:userCanAlreadyChangeSelection:] + 288 10 AppKit 0x00000001933176c4 -[NSTableView _userSelectRowIndexes:withNewSelectedRow:] + 140 11 AppKit 0x00000001933175a0 -[NSTableView _userSelectSingleRow:] + 76 12 AppKit 0x0000000193315c8c -[NSTableView mouseDown:] + 2536 13 AppKit 0x0000000193315120 -[NSOutlineView mouseDown:] + 72 14 MyApp 0x0000000100dabb38 -[CustomNSOutlineView mouseDown:] (CustomNSOutlineView.m:180) 15 AppKit 0x000000019320d98c forwardMethod + 248 16 AppKit 0x000000019320d98c forwardMethod + 248 17 AppKit 0x0000000193213518 -[NSWindow(NSEventRouting) _handleMouseDownEvent:isDelayedEvent:] + 3668 18 AppKit 0x000000019319f00c -[NSWindow(NSEventRouting) _reallySendEvent:isDelayedEvent:] + 380 19 AppKit 0x000000019319ecbc -[NSWindow(NSEventRouting) sendEvent:] + 280 20 AppKit 0x00000001939b6bf0 -[NSApplication(NSEventRouting) sendEvent:] + 1652 21 AppKit 0x00000001935c489c -[NSApplication _handleEvent:] + 56 22 AppKit 0x000000019306ab08 -[NSApplication run] + 516 23 AppKit 0x0000000193041364 NSApplicationMain + 884 24 MyApp 0x0000000100d0626c main (main.m:24) 25 ??? 0x000000018f0e4274 0x0 + 0 I just created a Feedback FB15625970. Please let me know if this is a known issue, and/or if there's any ideas out there on how I can do to avoid this. It's causing a lot of instability in my app, that wasn't there before macOS15, so something changed in the internal APIs, and hopefully there's a way to work around it.

Hi, When using SwiftUI ‘List’ with a large number of elements (4000+), I noticed a significant performance issue if extracting the views inside the ‘ForEach’ block into their own subview class. It affects scrolling performance, and using the scroll handle in the scrollbar causes stutters and beachballs. This seems to happen on macOS only ... the same project works fine on iOS. Here's an example of what I mean: List (selection: $multiSelectedContacts) { ForEach(items) { item in // 1. this subview is the problem ... replace it with the contents of the subview, and it works fine PlainContentItemView(item: item) // 2. Uncomment this part for it to work fine (and comment out PlainContentItemView above) /*HStack { if let timestamp = item.timestamp, let itemNumber = item.itemNumber { Text("\(itemNumber) - \(timestamp, formatter: itemFormatter)") } }*/ } } struct PlainContentItemView: View { let item: Item var body: some View { HStack { if let timestamp = item.timestamp, let itemNumber = item.itemNumber { Text("\(itemNumber) - \(timestamp, formatter: itemFormatter)") } } } } Item is a NSManagedObject subclass, and conforms to Identifiable by using the objectID string value. With this, scrolling up and down using the scrolling handle, causes stuttering scrolling and can beachball on my machine (MacBook Pro M1). If I comment out the ‘PlainContentItemView’ and just use the HStack directly (which is what was extracted to ‘PlainContentItemView’), the performance noticeably improves, and I can scroll up and down smoothly. Is this just a bug with SwiftUI, and/or can I do something to improve this?

In creating a sequenced gesture combining a LongPressGesture and a DragGesture, I found that the combined gesture exhibits two problems: The @GestureState does not properly update as the gesture progresses through its phases. Specifically, the updating(_:body:) closure (documented here) is only ever executed during the drag interaction. Long presses and drag-releases do not call the updating(_:body:) closure. Upon completing the long press gesture and activating the drag gesture, the drag gesture remains empty until the finger or cursor has moved. The expected behavior is for the drag gesture to begin even when its translation is of size .zero. This second problem – the nonexistence of a drag gesture once the long press has completed – prevents access to the location of the long-press-then-drag. Access to this location is critical for displaying to the user that the drag interaction has commenced. The below code is based on Apple's example presented here. I've highlighted the failure points in the code with // *. My questions are as follows: What is required to properly update the gesture state? Is it possible to have a viable drag gesture immediately upon fulfilling the long press gesture, even with a translation of .zero? Alternatively to the above question, is there a way to gain access to the location of the long press gesture? import SwiftUI import Charts enum DragState { case inactive case pressing case dragging(translation: CGSize) var isDragging: Bool { switch self { case .inactive, .pressing: return false case .dragging: return true } } } struct ChartGestureOverlay<Value: Comparable & Hashable>: View { @Binding var highlightedValue: Value? let chartProxy: ChartProxy let valueFromChartProxy: (CGFloat, ChartProxy) -> Value? let onDragChange: (DragState) -> Void @GestureState private var dragState = DragState.inactive var body: some View { Rectangle() .fill(Color.clear) .contentShape(Rectangle()) .onTapGesture { location in if let newValue = valueFromChartProxy(location.x, chartProxy) { highlightedValue = newValue } } .gesture(longPressAndDrag) } private var longPressAndDrag: some Gesture { let longPress = LongPressGesture(minimumDuration: 0.2) let drag = DragGesture(minimumDistance: .zero) .onChanged { value in if let newValue = valueFromChartProxy(value.location.x, chartProxy) { highlightedValue = newValue } } return longPress.sequenced(before: drag) .updating($dragState) { value, gestureState, _ in switch value { case .first(true): // * This is never called gestureState = .pressing case .second(true, let drag): // * Drag is often nil // * When drag is nil, we lack access to the location gestureState = .dragging(translation: drag?.translation ?? .zero) default: // * This is never called gestureState = .inactive } onDragChange(gestureState) } } } struct DataPoint: Identifiable { let id = UUID() let category: String let value: Double } struct ContentView: View { let dataPoints = [ DataPoint(category: "A", value: 5), DataPoint(category: "B", value: 3), DataPoint(category: "C", value: 8), DataPoint(category: "D", value: 2), DataPoint(category: "E", value: 7) ] @State private var highlightedCategory: String? = nil @State private var dragState = DragState.inactive var body: some View { VStack { Text("Bar Chart with Gesture Interaction") .font(.headline) .padding() Chart { ForEach(dataPoints) { dataPoint in BarMark( x: .value("Category", dataPoint.category), y: .value("Value", dataPoint.value) ) .foregroundStyle(highlightedCategory == dataPoint.category ? Color.red : Color.gray) .annotation(position: .top) { if highlightedCategory == dataPoint.category { Text("\(dataPoint.value, specifier: "%.1f")") .font(.caption) .foregroundColor(.primary) } } } } .frame(height: 300) .chartOverlay { chartProxy in ChartGestureOverlay<String>( highlightedValue: $highlightedCategory, chartProxy: chartProxy, valueFromChartProxy: { xPosition, chartProxy in if let category: String = chartProxy.value(atX: xPosition) { return category } return nil }, onDragChange: { newDragState in dragState = newDragState } ) } .onChange(of: highlightedCategory, { oldCategory, newCategory in }) } .padding() } } #Preview { ContentView() } Thank you!

I have a Catalyst app that uses popovers frequently, and I'd love to have them stay active when the app loses focus. It appears this is controlled in a native AppKit app via NSPopover.Behavior. Is this functionality exposed somewhere in Catalyst?

Basic Information Please provide a descriptive title for your feedback: Sheet presentationDetents breaks after rapid open/dismiss cycles Which platform is most relevant for your report? iOS Description Steps to Reproduce: Create a sheet with presentationDetents([.medium]) Rapidly perform these actions multiple times (usually 3-4 times): a. Open the sheet b. Immediately scroll down to dismiss Open the sheet again Observe that the sheet now appears at .large size, ignoring the .medium detent Expected Result: Sheet should consistently maintain .medium size regardless of how quickly it is opened and dismissed. Actual Result: After rapid open/dismiss cycles, the sheet ignores .medium detent and appears at .large size. Reproduction Rate: Occurs consistently after 3-4 rapid open/dismiss cycles More likely to occur with faster open/dismiss actions Configuration: iOS 18 Xcode 16.0 (16A242d) SwiftUI Device: iPhone 14

In Swift 6, stricter concurrency rules can lead to challenges when making SwiftUI views conform to Equatable. Specifically, the == operator required for Equatable must be nonisolated, which means it cannot access @MainActor-isolated properties. This creates an error when trying to compare views with such properties: Error Example: struct MyView: View, Equatable { let title: String let count: Int static func ==(lhs: MyView, rhs: MyView) -> Bool { // Accessing `title` here would trigger an error due to actor isolation. return lhs.count == rhs.count } var body: some View { Text(title) } } Error Message: Main actor-isolated operator function '==' cannot be used to satisfy nonisolated protocol requirement; this is an error in the Swift 6 language mode. Any suggestions? Thanks FB: FB15753655 (SwiftUI View cannot conform custom Equatable protocol in Swift 6.)

We're seeing sporadic crashes on devices running iOS 18.1 - both beta and release builds (22B83). The stack trace is always identical, a snippet of it below. As you can tell from the trace, it's happening in places we embed SwiftUI into UIKit via UIHostingController. Anyone else seeing this? 4 libobjc.A.dylib 0xbe2c _objc_fatalv(unsigned long long, unsigned long long, char const*, char*) + 30 5 libobjc.A.dylib 0xb040 weak_register_no_lock + 396 6 libobjc.A.dylib 0xac50 objc_storeWeak + 472 7 libswiftCore.dylib 0x43ac34 swift_unknownObjectWeakAssign + 24 8 SwiftUI 0xeb74c8 _UIHostingView.base.getter + 160 9 SwiftUI 0x92124 _UIHostingView.layoutSubviews() + 112 10 SwiftUI 0x47860 @objc _UIHostingView.layoutSubviews() + 36

I want to support Genmoji input in my SwiftUI TextField or TextEditor, but looking around, it seems there's no SwiftUI only way to do it? If none, it's kind of disappointing that they're saying SwiftUI is the path forward, but not updating it with support for new technologies. Going back, does this mean we can only support Genmoji through UITextField and UIViewRepresentable? or there more direct options? Btw, I'm also using SwiftData for storage.

When call: [UITabBarController setViewControllers:animated:] It crashed and raise an Fatal Exception: Fatal Exception: NSInternalInconsistencyException Attempting to select a view controller that isn't a child! (null) the crash stack is: Fatal Exception: NSInternalInconsistencyException 0 CoreFoundation 0x8408c __exceptionPreprocess 1 libobjc.A.dylib 0x172e4 objc_exception_throw 2 Foundation 0x82215c _userInfoForFileAndLine 3 UIKitCore 0x38a468 -[UITabBarController transitionFromViewController:toViewController:transition:shouldSetSelected:] 4 UIKitCore 0x3fa8a4 -[UITabBarController _setSelectedViewController:performUpdates:] 5 UIKitCore 0x3fa710 -[UITabBarController setSelectedIndex:] 6 UIKitCore 0x8a5fc +[UIView(Animation) performWithoutAnimation:] 7 UIKitCore 0x3e54e0 -[UITabBarController _setViewControllers:animated:] 8 UIKitCore 0x45d7a0 -[UITabBarController setViewControllers:animated:] And it appear sometimes, what's the root cause?

I'm trying to figure out how to make an inverted list in my watchOS app for a message view, so that messages appear from the bottom first, and go up. Everything I've tried so far has some sort of major drawback, and I'm wondering if there's some proper way to do it. My current implementation is flipping every message item upside-down, then flipping the whole list upside-down. This works in making the list go from bottom to top, but the digital crown scroll direction is also inverted. Simply inverting the array of messages doesn't work either, as the user has to scroll to the bottom of the list manually every time. Any tips/suggestions would be greatly appreciated.

Hi, I've created an carousel using an Tabview component and it is divided in pages, each page has 7 items. Now we wan't to load the carousel page by page, but whenever I updated the list which Tabview uses to render, it flickers because it rerenders previous elements. I've tried to use a scroll view for this but this app is for Vision Pro and I added some 3D transformations (position/rotation) to the cards from the tabview and when I added this in the scrollview they becom unclickable. Do you have any sugestions what can I do? Bellow is a sample of the code, I put [items] just to suggest there is a list. VStack (spacing: 45) { TabView(selection: $navigationModel.carouselSelectedPage) { let orderedArtist = [items] let numberOfPages = Int((Double(orderedArtist.count) / Double(cardsPerPage)).rounded(.up)) if(numberOfPages != 1){ Spacer().tag(-1) } ForEach(0..<numberOfPages, id: \.self) { page in LazyHStack(alignment: .top, spacing: 16){ ForEach(0..<cardsPerPage, id: \.self) { index in if(page * cardsPerPage + index < orderedArtist.count){ let item = orderedArtist[page * cardsPerPage + index] GeometryReader{proxy in

Hi! So while Date is supported for @Parameter in an App Intent, I just discovered that Xcode will not let me use use it in a parametrized App Shortcut phrase. In my case, I would like to give the option to say "today", tomorrow", or "day after tomorrow" for the date. Am I missing something? Any hints on the best way to approach this?

I have an iOS Widget that also can load on the Mac when the Use iPhone Widgets setting is turned on on the Mac in Desktop & Dock. I want to use a different url scheme to open video clips from the widget if it is being clicked on iOS or the Mac. I tried using ProcessInfo.processInfo.isiOSAppOnMac but it always thinks it is on iOS. I also tried looking for the user document path to see if it was /var/mobile/ or /Users/. but it always thinks it is /var/mobile. I assume this is as it is not really a catalyst app but a WidgetKit extension from the phone. Is there anyway I can figure out when the widget is running on the mac? Thanks!

Hello, I have the following code: struct SettingsButton: View { var action: () -> Void @State private var rotate: Bool = false var body: some View { Button(action: { rotate.toggle() action() }, label: { Image(systemName: "gearshape") }) .symbolEffect(.rotate, value: rotate) } } For some reason, my button is not rotating. Other effects such as pulse and bounce work as expected. I applied the .clockwise direction thinking it needed a direction set, but that didn't work either. I also tried using the symbolEffect with isActive, and that didn't work. Lastly, I thought there may be an issue with Xcode so I closed that and reopened, but still not working. Any ideas?

Is there any way to prevent the keyboard from bouncing when changing the focus state in onSubmit? Or is it not recommended to change focus in onSubmit? The following view is setup so that pressing return on the keyboard should cause focus to move between the TextFields. struct TextFieldFocusState: View { enum Field { case field1 case field2 } @FocusState var focusedField: Field? var body: some View { Form { TextField("Field 1", text: .constant("")) .focused($focusedField, equals: .field1) .onSubmit { focusedField = .field2 } TextField("Field 2", text: .constant("")) .focused($focusedField, equals: .field2) .onSubmit { focusedField = .field1 } } } } I would expect that when pressing return, the keyboard would say on screen. What actually happens is the keyboard appears to bounce when the return key is pressed (first half of gif). I assume this is because onSubmit starts dismissing the keyboard then setting the focus state causes the keyboard to be presented again. The issue doesn't occur when tapping directly on the text fields to change focus (second half of gif).

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?