The ios app I am currently developing starts off on a login screen which then presents the next view controller via a login button. Upon moving on to the next VC I get the error: Terminating app due to uncaught exception 'NSGenericException', reason: 'Unable to activate constraint with anchors <NSLayoutYAxisAnchor:0x600000d0af40 "UIStackView:0x7fe87df14160.top"> and <NSLayoutYAxisAnchor:0x600000d0ad40 "UILayoutGuide:0x600002102300'UIViewSafeAreaLayoutGuide'.bottom"> because they have no common ancestor. Does the constraint or its anchors reference items in different view hierarchies? That's illegal.' Here is the relevant VC code for the contoller being showed: class LocationSelectViewController: UIViewController {       let promptLabel: UILabel = {     let label = UILabel()           label.translatesAutoresizingMaskIntoConstraints = false     label.text = "Enter Your Location`s \nAddress"     label.font = .boldSystemFont(ofSize: 23)     label.numberOfLines = 0     label.preferredMaxLayoutWidth = label.frame.width     label.textAlignment = .center           return label   }()       let streetAddressField: UITextField = {     let textField = UITextField()         textField.translatesAutoresizingMaskIntoConstraints = false     textField.placeholder = "street address"     textField.borderStyle = .roundedRect     textField.textAlignment = .left         return textField   }()       let cityField: UITextField = {     let textField = UITextField()         textField.translatesAutoresizingMaskIntoConstraints = false     textField.placeholder = "city"     textField.borderStyle = .roundedRect     textField.textAlignment = .left         return textField   }()       let stateField: UITextField = {     let textField = UITextField()         textField.translatesAutoresizingMaskIntoConstraints = false     textField.placeholder = "state"     textField.borderStyle = .roundedRect     textField.textAlignment = .left         return textField   }()       let saveButton: UIButton = {     let button = UIButton(type: .system)     button.setTitle("Add Location", for: .normal)     button.translatesAutoresizingMaskIntoConstraints = false           return button   }()       var currentUser: User?   let geocoder = CLGeocoder()   override func viewDidLoad() {     super.viewDidLoad()           view.backgroundColor = .white           let stackView = UIStackView()           let views: [UIView] = [streetAddressField, cityField, stateField]           stackView.axis = .vertical     stackView.spacing = 17     stackView.translatesAutoresizingMaskIntoConstraints = false           view.addSubview(promptLabel)     view.addSubview(stackView)     view.addSubview(saveButton)           for view in views {       stackView.addArrangedSubview(view)     }           let constraintsArray: [NSLayoutConstraint] = [promptLabel.centerXAnchor.constraint(equalTo: view.safeAreaLayoutGuide.centerXAnchor), promptLabel.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 30), promptLabel.heightAnchor.constraint(lessThanOrEqualToConstant: 70), stackView.topAnchor.constraint(equalTo: promptLabel.bottomAnchor, constant: 40), stackView.centerXAnchor.constraint(equalTo: view.safeAreaLayoutGuide.centerXAnchor), stackView.widthAnchor.constraint(equalToConstant: 300), saveButton.centerXAnchor.constraint(equalTo: view.safeAreaLayoutGuide.centerXAnchor), saveButton.topAnchor.constraint(equalTo: stackView.bottomAnchor, constant: 30)]           saveButton.addTarget(self, action: #selector(addLocationTouchUpInside), for: .touchUpInside)           NSLayoutConstraint.activate(constraintsArray)   } Also I am aware that the constraints are hard to read so they are listed below promptLabel.centerXAnchor.constraint(equalTo: view.safeAreaLayoutGuide.centerXAnchor), promptLabel.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 30), promptLabel.heightAnchor.constraint(lessThanOrEqualToConstant: 70), stackView.topAnchor.constraint(equalTo: promptLabel.bottomAnchor, constant: 40), stackView.centerXAnchor.constraint(equalTo: view.safeAreaLayoutGuide.centerXAnchor), stackView.widthAnchor.constraint(equalToConstant: 300), saveButton.centerXAnchor.constraint(equalTo: view.safeAreaLayoutGuide.centerXAnchor), saveButton.topAnchor.constraint(equalTo: stackView.bottomAnchor, constant: 30) I orginally asked this question on SO which has lead me to believe this is a potential bug. I likely could hold off or workaround the issue by rewriting/choosing different constraints, but if its a bug I would much rather not put in pointless work.

Using NSCollectionLayoutSize with .estimated dimensions in horizontal orthogonal sections, creates layout issues. The cells &amp; supplementary views have layout conflicts, the scroll behavior is sub optimal and spacing is not as expected Working with Xcode: 12.4 , Simulator: iOS 14.4 Layout bug: [LayoutConstraints] Unable to simultaneously satisfy constraints. Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. ( "NSLayoutConstraint:0x6000011266c0 UIView:0x7fc6c4617020.height == 80 (active)", "NSLayoutConstraint:0x600001126530 V:|-(0)-[UIView:0x7fc6c4617020] (active, names: '|':UIView:0x7fc6c4616d10 )", "NSLayoutConstraint:0x6000011261c0 UIView:0x7fc6c4617020.bottom == UIView:0x7fc6c4616d10.bottom (active)", "NSLayoutConstraint:0x600001121360 'UIView-Encapsulated-Layout-Height' UIView:0x7fc6c4616d10.height == 50 (active)" ) Will attempt to recover by breaking constraint NSLayoutConstraint:0x6000011266c0 UIView:0x7fc6c4617020.height == 80 (active) Code to reproduce: import UIKit class ViewController: UIViewController { lazy var collectionView: UICollectionView = { let layout = createLayout() let collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout) collectionView.translatesAutoresizingMaskIntoConstraints = false collectionView.dataSource = self collectionView.backgroundColor = .systemBackground collectionView.register(Cell.self, forCellWithReuseIdentifier: "cell") collectionView.register(HeaderView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: "header") return collectionView }() private func createLayout() - UICollectionViewCompositionalLayout { let sectionProvider = { (section: Int, layoutEnvironment: NSCollectionLayoutEnvironment) - NSCollectionLayoutSection? in return self.horizontalLayout(layoutEnvironment: layoutEnvironment) } let config = UICollectionViewCompositionalLayoutConfiguration() config.interSectionSpacing = 8 let layout = UICollectionViewCompositionalLayout(sectionProvider: sectionProvider, configuration: config) return layout } private func supplementaryHeader() - NSCollectionLayoutBoundarySupplementaryItem { let titleSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1.0), heightDimension: .estimated(50)) let titleSupplementary = NSCollectionLayoutBoundarySupplementaryItem( layoutSize: titleSize, elementKind: UICollectionView.elementKindSectionHeader, alignment: .top) return titleSupplementary } private func horizontalLayout(layoutEnvironment: NSCollectionLayoutEnvironment) - NSCollectionLayoutSection { let size = NSCollectionLayoutSize(widthDimension: .estimated(120), heightDimension: .estimated(50)) let item = NSCollectionLayoutItem(layoutSize: size) let group = NSCollectionLayoutGroup.horizontal(layoutSize: size, subitems: [item]) let section = NSCollectionLayoutSection(group: group) section.orthogonalScrollingBehavior = .continuous section.interGroupSpacing = 8 section.contentInsets = NSDirectionalEdgeInsets(top: 16, leading: 16, bottom: 16, trailing: 16) section.boundarySupplementaryItems = [supplementaryHeader()] return section } override func viewDidLoad() { super.viewDidLoad() view.addSubview(collectionView) NSLayoutConstraint.activate([ collectionView.leadingAnchor.constraint(equalTo: view.leadingAnchor), collectionView.trailingAnchor.constraint(equalTo: view.trailingAnchor), collectionView.topAnchor.constraint(equalTo: view.topAnchor), collectionView.bottomAnchor.constraint(equalTo: view.bottomAnchor) ]) } } // MARK: UICollectionViewDataSource extension ViewController: UICollectionViewDataSource { func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) - UICollectionViewCell { let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) return cell } func numberOfSections(in collectionView: UICollectionView) - Int { return 25 } func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) - Int { return 4 } func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) - UICollectionReusableView { switch kind { case UICollectionView.elementKindSectionHeader: let header: HeaderView = collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: "header", for: indexPath) as! HeaderView return header default: fatalError() } } } class Cell: UICollectionViewCell { lazy var view: UIView = { let view = UIView() view.translatesAutoresizingMaskIntoConstraints = false view.backgroundColor = .systemRed return view }() override init(frame: CGRect) { super.init(frame: frame) configure() } required init?(coder: NSCoder) { fatalError("not implemented") } func configure() { contentView.addSubview(view) view.heightAnchor.constraint(equalToConstant: 80).isActive = true view.widthAnchor.constraint(equalToConstant: 100).isActive = true NSLayoutConstraint.activate([ view.leadingAnchor.constraint(equalTo: contentView.leadingAnchor), view.trailingAnchor.constraint(equalTo: contentView.trailingAnchor), view.topAnchor.constraint(equalTo: contentView.topAnchor), view.bottomAnchor.constraint(equalTo: contentView.bottomAnchor) ]) } } class HeaderView: UICollectionReusableView { lazy var view: UIView = { let view = UIView() view.translatesAutoresizingMaskIntoConstraints = false view.backgroundColor = .systemTeal return view }() override init(frame: CGRect) { super.init(frame: frame) configure() } required init?(coder: NSCoder) { fatalError("not implemented") } func configure() { addSubview(view) view.heightAnchor.constraint(equalToConstant: 60).isActive = true NSLayoutConstraint.activate([ view.leadingAnchor.constraint(equalTo: self.leadingAnchor), view.trailingAnchor.constraint(equalTo: self.trailingAnchor), view.topAnchor.constraint(equalTo: self.topAnchor), view.bottomAnchor.constraint(equalTo: self.bottomAnchor) ]) } }

This is really a post (dig at) to the SwiftUI designers. I have been a developer in many many different languages for far too many years. Over the last 20 I have done a lot of web (browser) development. From the web developer perspective, developing applications that behave correctly in any browser has been a really big thing for probably more than 20 years. I even remember doing it in tables. We are now at a stage where it does work now (mostly). Frameworks like Twitter Bootstrap work really well and so do a lot of others. Their basic mission is that a page (view) will work no matter what the resolution (even those we don’t have yet) in an ever changing ‘view’ world. Yet I now come to SwiftUI… Lots of tell us your device and get your graphic designer to produce a zillion graphics for each (noting he / she isn’t a fortune teller, so they do not know what’s coming next. After playing for days with GeometryReader and UIScreen.main.bounds (hell will that even be supported in the future) I’m not impressed. I don’t understand why something that has been analysed and pretty much put to bed in the ‘web’ world is now attempting to be reinvented really really really really badly. I even attempted to fix this issue with UIKit but even that wasn’t much better.  Why is a company with so much money and so many resources trying to reinvent the wheel? I don’t get it. So much so I’m starting to tell my clients (big ones) to ditch Apple and go down far easier roots. I doubt any of the SwiftUI compiler developers even read this stuff. But hey if you do, it’s time for a reality check… If they don’t ha ha ha ha I rest my case.

Hi! How can I create a self sizing collectionview cells in section via UiCollectionViewCompositionalLayout? Thanks!

Hello! I am new to iOS development and was walking through UIKit iOS App Dev Tutorial on this website. My problems start every time when I need to set leading horizontal spacing to "Standard" by removing value or selecting it in the dropdown menu. When I try to do that, the value in the field resets to previously set value and "Use Standard value" is greyed out. This is so frustrating! Even when I download complete project and try to set value myself, it still does not work! Is it an Xcode bug? My version is 13.0 (13A233)

Hello! I am having trouble with my quiz game - sometimes (not always) after completing a level, the screen darkens and the game becomes unresponsive. I am unable to click anywhere on the screen. I've been scratching my head about this issue for several weeks now and can't get to the bottom of it. I'd really appreciate some help/advice on the matter if anyone knows that's wrong. I've attached the error log as it was too long to add here. Many thanks, Ermes Error log:

CoreAutoLayout: _AssertAutoLayoutOnAllowedThreadsOnly + 412 Please can anyone help me

Hey, When I use boundingRect with String, and supply .usesFontLeading as one of the options, I get an inaccurate height for some reason. Why is that?

In the context of UILabel, If I were to calculate the height of the content I'm displaying... is it better to use textRect or boundingRect?

I'm using boundingRect to calculate the height of a String, I'm using Ubuntu as my font, and when I supply .usesFontLeading as one of the options alongside .usesLineFragmentOrigin the height is completely different to what I expect. Here is the code I'm using for reference: func height(withConstrainedWidth width: CGFloat, font: UIFont, maxLines: CGFloat = 0) -> CGFloat {         let constraintRect = CGSize(width: width, height: .greatestFiniteMagnitude)         let boundingBox = self.boundingRect(with: constraintRect, options: [.usesFontLeading, .usesLineFragmentOrigin], attributes: [             NSAttributedString.Key.font: font         ], context: nil)         var size = boundingBox.size         if maxLines > 0 {             size.height = min(size.height, CGFloat(maxLines) * font.lineHeight)         }         return ceil(size.height)     } Firstly, what does .usesFontLeading even do, and why is it that the result I'm getting an unexpected result. Note: self is String because I've extended the String class.

I've constrained a UILabel to leading, and trailing anchors, the intrinsicContentSize exceeds the anchors I've specified. Just to be sure, I added a widthAnchor as well, still no improvement. Then I added these properties: self.preferredMaxLayoutWidth = 356.25 // didn't hard code self.invalidateIntrinsicContentSize() Still the intrinsicContentSize is equal to 356.5, which is something I don't expect from my UILabel, is there anyway to fix this issue?

I'm experiencing an intermittent bug with Auto Layout in the popover for Safari App Extensions. It appears that any resizing in the view controller sometimes happens before the window itself is resized, and this has a very odd appearance. I'd like to figure out how to stop this from happening. I've tried moving any constraint changes into the updateConstraints method as suggested in AppKit resources I've found, however the bug remains. For reference, here are the collapsed and expanded views: Here are the intermediate frames that I'd like to prevent: This is the function that toggles the constraints to show/hide the long text: @objc private func toggleContent(_ sender: NSButton) { if longText.isDescendant(of: contentView) { contentButton.title = "Show text" // Remove text longText.removeFromSuperview() initialBottomConstraint.isActive = true } else { // Add text contentButton.title = "Hide text" initialBottomConstraint.isActive = false longText.translatesAutoresizingMaskIntoConstraints = false contentView.addSubview(longText) NSLayoutConstraint.activate([ longText.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 16.0), longText.topAnchor.constraint(equalTo: contentButton.bottomAnchor, constant: 16.0), longText.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: -16.0), longText.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: -16.0) ]) } } Edit: for screenshot size

Hello I've been trying to build our existing iOS 14 app using Xcode 13 beta 5, and though it was working perfectly before, when trying to display some of the views on our main page this exception is consistently raised when trying to apply a snapshot on a UITableViewDiffableDataSource: Must translate autoresizing mask into constraints. looking online it seems that in previous Xcode betas have had this issue in relation to table view cells. Has anyone else been seeing this when trying to build with iOS 15? Thanks

hi! I'm beginner ios developer. I have a question about auto layout problem on Display Zoomed ( setting - Display & Brightness - Display Zoom - Zoomed) standard mode not occur problem. but user set Display Zoomed UILabel_1 covers UILabel_2 I think that UILabel_2 has constrant(Bottom space to : Button 30) finally, I Want this image. if user set Display Zoomed, if Display Zoomed mode, UILabel_2 can constrant? thank you

Hello, Please help me solve this error: IB Designables: Failed to render and update auto layout status for ViewController (BYZ-38-t0r): dlopen(Demo.app, 1): no suitable image found. Did find: Demo.app: mach-o, but not built for platform iOS-sim I create new simple application. Then I create custom view with IB Designables and this broke Storyboard. I have a lot of projects in which I use Storyboard and now I cannot edit them. Thanks. Xcode: 12.5.1 (12E507) MacOS: 11.5.1 (20G80) Chip: Apple M1

I am using a UIView with a nib as a template for a UIImage that I am generating, and I want to handle the output of the iPad in landscape differently than portrait. The best way I have figured I can do that is by setting up my landscape view for horizontal Regular, vertical Compact traits in the nib and assigning those traits before generating the image. I have tried using the performAsCurrent method which successfully changes the UITraitCollection.current value but does not affect my UIView traitCollection property, and I have tried overriding the traitCollection getter in the UIView class which returns the error: Class overrides the -traitCollection getter, which is not supported. If you're trying to override traits, you must use the appropriate API. Is there a way to do this for a UIView that is never drawn to the screen?

I want to build Instagram like comment - replies UI. Here are few questions. 1 - Nested CollectionView. I first built comments UI with collectionView. But now facing self-cell sizing issue on how to update the height of cell dynamically based on the nested collectionView of replies. 2 - Nested Tableview. So I thought maybe with automatic dimension set up with tableview. It'd be much simpler to build comment-replies UI. But I read on Stack Overflow that nested tableViews are not recommended because it might mess up with scrolls . 3 - So what would be the best way to build comment-replies UI just like Instagram?