I am getting a strange error with iOS13 when performing a Segue and I can't figure out what it means, nor can I find any documentation for this error. The problem is that this seems to cause a lot of lag (a few seconds) until the segue is performed.
2019-09-11 22:45:38.861982+0100 Thrive[2324:414597] [TableView] Warning once only: UITableView was told to layout its visible cells
and other contents without being in the view hierarchy (the table view
or one of its superviews has not been added to a window). This may
cause bugs by forcing views inside the table view to load and perform
layout without accurate information (e.g. table view bounds, trait
collection, layout margins, safe area insets, etc), and will also
cause unnecessary performance overhead due to extra layout passes.
Make a symbolic breakpoint at
UITableViewAlertForLayoutOutsideViewHierarchy to catch this in the
debugger and see what caused this to occur, so you can avoid this
action altogether if possible, or defer it until the table view has
been added to a window. Table view: ; layer = ; contentOffset: {0, 0}; contentSize: {315, 118};
adjustedContentInset: {0, 0, 0, 0}; dataSource: >
I am using Hero but I tried disabling it and using a regular Segue and this hasn't stopped the lag.
The code to initiate the segue is didSelectRowAt
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
if indexPath.section == 0 {
selectedCell = realIndexFor(activeGoalAt: indexPath)
performSegue(withIdentifier: "toGoalDetails", sender: nil)
} else if indexPath.section == 1 {
selectedCell = indexPath.row
performSegue(withIdentifier: "toIdeaDetails", sender: nil)
} else {
selectedDecision = indexPath.row
hero(destination: "DecisionDetails", type: .zoom)
}
}
And then none of the code in viewDidLoad or viewWillAppear from the destination VC affects this in any way (I tried commenting it all out with no difference.
Any idea what's causing this? I can share whatever other details are needed.
Thank you.
It happened to me because I registered the device for change orientation notification in the viewWillAppear(:) method.
I moved the registration in the viewDidAppear(:) and Xcode it's not stopping at the breakpoint anymore.
What I can say is that layout changes might be run when the view is already visible...
For people using DiffableDataSource, set animatingDifferences to false and warning will be gone.
dataSource.apply(snapshot, animatingDifferences: false)
Like #joe-h, I was getting this error and was also surprised as the unwind approach he shows is one used by lots of developers + is in some significant Apple iOS sample code.
The triggering line in my code (#joe-h, I'm guessing likely in yours, too) is a tableView.reloadRows at the selectedIndexPath (which is an unwrapped tableView.indexPathForSelectedRow):
tableView.reloadRows(at: [selectedIndexPath], with: .automatic)
Unfortunately commenting out the row isn't an option if you are unwinding after updating the value in an existing tableView row (which is an approach in the Apple FoodTracker tutorial mentioned above, as well as one used in Apple's Everyone Can Code series). If you don't reload the row(s) then your change won't show in the tableView. After commenting out the reload in the unwind, I added a viewDidAppear with the following code and this seems to fix things:
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
if let selectedIndexPath = tableView.indexPathForSelectedRow {
tableView.reloadRows(at: [selectedIndexPath], with: .automatic)
}
}
I'd welcome comments on whether this is a sound approach, but for now, this seems to be working.
I had the same error on my Project; A tableView with a diffable datasource. Been bugging on it for hours. Problem lies in updating the snapshot, more specifically on a background thread (default). Forcing the update of the datasource on the main thread got rid of the problem! Hope this helps someone out there!
func updateData(on annotations: [Annotation]) {
var snapshot = NSDiffableDataSourceSnapshot<AnnotationType, Annotation>()
//Append available sections
AnnotationType.allCases.forEach { snapshot.appendSections([$0]) }
//Append annotations to their corresponding sections
annotations.forEach { (annotation) in
snapshot.appendItems([annotation], toSection: annotation.type as AnnotationType)
}
//Force the update on the main thread to silence a warning about tableview not being in the hierarchy!
DispatchQueue.main.async {
self.dataSource.apply(snapshot, animatingDifferences: true)
}
}
This warning can happen du to updating table view or collection view while it is not visible, for example when it is on the parent view controller. To solve that, first, I created a property in the view controller, containing the table view to check if the view controller is visible or not, as bellow:
var isVisible: Bool = false
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
self.isVisible = true
}
override func viewDidDisappear(_ animated: Bool) {
super.viewDidAppear(animated)
self.isVisible = false
}
Then in the data source delegate, before reacting to changes, first check if the view controller is visible. If it was not, do not do any updates. For example
func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
guard isVisible else { return }
tableView.beginUpdates()
}
You should check that visibility before doing any changes in the tableView. For example, in case of NSFetchedResultsController, it must be done in all delegate callbacks which we have implemented.
UPDATE
I recently found that if you update the table view with animation false, even when it is not visible, there won't be any warnings.
I'm new to Xcode/Swift so this may or may not help anyone. I started getting this error after updating to iOS 13 and Xcode 11 within the app when going back to a list from a detail view.
I found that I was doing a tableView.reloadRows and tableView.insertRows in the unwind(as suggested by Apple in one of their tutorials)
#IBAction func unwindToMealList(sender: UIStoryboardSegue) {
if let sourceViewController = sender.source as? MealViewController, let meal = sourceViewController.meal {
if let selectedIndexPath = tableView.indexPathForSelectedRow {
// Update an existing meal.
meals[selectedIndexPath.row] = meal
tableView.reloadRows(at: [selectedIndexPath], with: .none)
}
else {
// Add a new meal.
let newIndexPath = IndexPath(row: meals.count, section: 0)
meals.append(meal)
tableView.insertRows(at: [newIndexPath], with: .automatic)
}
}
}
)
I commented out that section of code and it went away.
Oddly enough leaving the sort and self.tableView.reloadData() didn't give me the error.
In viewDidDisappear method I declare tableView.setContentOffset(CGPoint(x: 0, y: 0), animated: false) function. Some of you says it's not important but it affected tableView delegate methods. For example viewForHeader function is not called when I get this warning.
I found the most robust and safe way is to wait for the didMoveToWindow of the table view / collection view
as even in viewWillAppear the view may NOT be attached to a window and puting your code in viewDidAppear may cause unwanted graphical glitches
class MyTableViewOrCollectionView: UITableView {
var didMoveToWindowCallback: (()->())? = nil
override func didMoveToWindow() {
super.didMoveToWindow()
didMoveToWindowCallback?()
didMoveToWindowCallback = nil
}
}
and than you can
override func viewDidLoad() {
super.viewDidLoad()
tableView.didMoveToWindowCallback = { [weak self] in
self?.setupInitialContent()
}
}
iPadOS 13.2.3 swift 5.2 Xcode 11.2.1
Just ran into this issue only when starting the app while the device was landscape.
I was calling the detail seque in the viewDidLoad func of the master controller to make sure the detail view was setup correctly.
override func viewDidLoad() {
super.viewDidLoad()
...
self.performSegue(withIdentifier: "showDetail", sender: self)
}
When I removed the performSeque the warning not longer appeared, however,
the left bar buttons on the detail controller no longer worked properly, again only when starting the app while the device was landscape. The left most button would activate the next button to the right instead of what the first button was suppose to do.
The fix for the bar buttons was to add to the viewDidLoad
override func viewDidLoad() {
super.viewDidLoad()
...
self.splitViewController?.preferredDisplayMode = UISplitViewController.DisplayMode.allVisible
}
Then execute
override func viewWillAppear(_ animated: Bool) {
self.splitViewController?.preferredDisplayMode = UISplitViewController.DisplayMode.automatic
super.viewWillAppear(animated)
}
I have no explanation why this worked!
This app had worked flawlessly until iPados 13 was loaded.
I am getting similar breakpoint with SwiftUI, without even dealing with viewDidLoad or viewDidappear
//
// ContentView.swift
// DD
//
// Created by Roman Emperor on 3/29/20.
// Copyright © 2020 Emperors. All rights reserved.
//
import Combine
import SwiftUI
// Defining a class Booking of type Bindable Object [changed to ObservableObject]
class Booking: ObservableObject {
var didChange = PassthroughSubject<Void, Never>()
// Array of types to work with
static let types = ["Consultation", "Tooth Pain", "Cleaning", "Brases", "Dental Implant" ]
// Setting instance varibale type
var type = 0 { didSet { update() } }
func update () {
didChange.send(())
}
}
struct ContentView: View {
#ObservedObject var booking = Booking() //bindableObject in old swift version
var body: some View {
NavigationView {
Form {
Section {
Picker(selection: $booking.type, label: Text("Select a Booking Type")) {
ForEach(0 ..< Booking.types.count){
Text(Booking.types[$0]).tag($0)
}
}
}
}
.navigationBarTitle(Text("Darpan Dental Home"))
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
The Complete output Log is here:
*> 2020-03-29 09:22:09.626082+0545 DD[1840:76404] [TableView] Warning
once only: UITableView was told to layout its visible cells and other
contents without being in the view hierarchy (the table view or one of
its superviews has not been added to a window). This may cause bugs by
forcing views inside the table view to load and perform layout without
accurate information (e.g. table view bounds, trait collection, layout
margins, safe area insets, etc), and will also cause unnecessary
performance overhead due to extra layout passes. Make a symbolic
breakpoint at UITableViewAlertForLayoutOutsideViewHierarchy to catch
this in the debugger and see what caused this to occur, so you can
avoid this action altogether if possible, or defer it until the table
view has been added to a window.*
**where is this UITableViewAlertForLayoutOutsideViewHierarchy in SwiftUI ? **
extension UIView {
func rootView() -> UIView {
var view = self
while view.superview.isNotNil {
view = view.superview!
}
return view
}
var isOnWindow: Bool {
return self.rootView() is UIWindow
}
}
then you just need to check if your tableView isOnWindow like...
if self.tableView.isOnWindow {
/// do stuff
}
Disclaimer: as the documentation explains, you may need to defer the call which means that there is no warranty your method will be called again so it's your responsibility to perform your update when isOnWindow is true.
Had the same issue, removing tableView.reloadSections fixed it. This was the line of code causing the warning:
iOS 13:
tableView.reloadSections(IndexSet(integer: 0), with: .automatic)
in iOS 14, removing tableView.reloadSections did not fix the warning.
Or maybe your code (like mine) has nothing wrong with it and this message just randomly starts popping up. In that case, do a clean on your project, restart Xcode and watch the message magically go away!
Please check following function
override func viewWillLayoutSubviews()
For anyone that has this issue with a UISplitViewController and a UITableView inside the detail view controller, you can try subclassing and override layoutSubviews like this (From this thread):
class CustomTableView: UITableView {
override func layoutSubviews() {
if (self.window == nil) {
return
}
super.layoutSubviews()
}
}
Instead of reloading the rows inside viewDidAppear, this is what it worked for me:
DispatchQueue.main.asyncAfter(deadline: .now() + 0.2) {
self.tableView.reloadRows(at: [indexPath], with: .none)
}
Also if you are using DiffableDataSource and you are selecting an indexPath manually for example, you need to do it on the completion block of the apply snapshot method:
dataSource.apply(snapshot, to: section, animatingDifferences: false, completion: {
// select the indexPath programmatically or do UITableView UI stuff here.
})
... the table view or one of its superviews has not been added to a window ...
To resolve the issue we need to check tableView.window property:
class MyViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
updateTableViewRows()
}
func dataChanged() {
updateTableViewRows()
}
func updateTableViewRows() {
if tableView.window == nil {
// TODO: just update data source
} else {
tableView.performBatchUpdates {
// TODO: update data source
// TODO: update table view cells
}
}
}
}
The idea is to not call performBatchUpdates and related functions while tableView.window is nil.
I am relatively new on firebase. I want to update existing data on my firebase database. I have UITableView and UITableViewCells on my Xcode project, when user touch (tap gesture), for example a outlet on cell view, I want to update Firebase Database but this could be any cell on tableview. How to find this cell which user touched on screen, on firebase database and update its messageVoteScore value. There are assigned keys but my cells do not know those keys,
I could not figure it out how to match them.(Database/Messages/{"sender": "email"},{"messageBody":"text.."},{"messageVoteScore":"100"}
#objc func voteUpTapped(sender: UITapGestureRecognizer) {
// Update score //
self.messageVoteScore.text = String(Int(self.messageVoteScore.text!)! + 1 )
//observeSingleEventOfType listens for a tap by the current user.
Database.database().reference().child("Messages").observe(.value){
(snapshot) in
if let snapshotValue = snapshot.value as? [String : String] {
print(snapshotValue)
}
}
}
Are you passing class objects to your cell? If so you could use a protocol/delegate for this. A UITableView Cell is a View and shouldn't function as a controller. your UITableViewController should be updating firebase.
you should start by adding something like this to the top of your Cell class:
protocol MyTableViewCellDelegate: class {
func thingDidDo(object: Object, text: String...) //object is the class object you are changing.
then add the delegate to your properties:
weak var delegate: MyTableViewCellDelegate?
then add the IBAction:
#IBAction func thingDidDo(_ sender: Any) {
delegate?.thingDidDo(object: object, text: textView.text...)
}
Now back to your viewController Class:
In your "cellForRowAt" write in the delegate:
cell.delegate = self
then add an extension
extension MyTableViewController: MyTableViewCellDelegate {
func thingDidDo(object: Object, text: String) {
Do whatever you want with object, text...
}
Not sure what kind of function you are trying to perform so I made this as generic as I could
I am trying to perform a segue from another class via a class function.
I have a class called MyTableViewController. In that class I have constructed a view controller of the type AnswerViewController. A segue to this view controller is supposed to occur when a condition in the Extension : MyCell is met. The problem that I am having is that the function showNextView is not being called.
I have read posts on both Perform Segue From Another Swift File via a class function and Perform Segue from another class with helper function, but both of these create a segue before constructing the view controller (which I cannot do because I am not using storyboards and do not actually have segues, only pushViewController).
class MyTableViewController: UITableViewController {
//Construct View Controller
let answerViewController = AnswerViewController()
//Create goToNextView function which will be called in extension MyCell
func goToNextView(){
navigationController?.pushViewController(answerViewController, animated: true)
}
}
extension MyCell: YSSegmentedControlDelegate{
func segmentedControl(_ segmentedControl: YSSegmentedControl, willPressItemAt index: Int) {
tagToIndex[actionButton.tag] = index
print(tagToIndex)
//Condition To Be Met
if tagToIndex == [0:1,1:0,2:1]{
//Access function goToNextView from MyTableViewController
func showNextView(fromViewController : MyTableViewController){
fromViewController.goToNextView()
}
}
}
}
How do I call the showNextView function so that the segue occurs?
Thanks,
Nick
You can't do this that way. Your showNextView function is nested inside segmentedControl(_, willPressItemAt) - this means it is not accessible outside of it. You generally shouldn't use nested functions.
To solve your issue you should create a delegate for your cell and inform your view controller that an action has occured.
A simple example :
protocol MyCellDelegate: class {
func myCellRequestedToOpenAnswerVC(cell: MyCell)
}
class MyCell {
weak var delegate: MyCellDelegate?
// rest of your inplementation
}
Then, change segmentedControl(_, willPressItemAt) to :
func segmentedControl(_ segmentedControl: YSSegmentedControl, willPressItemAt index: Int) {
tagToIndex[actionButton.tag] = index
print(tagToIndex)
//Condition To Be Met
if tagToIndex == [0:1,1:0,2:1]{
self.delegate?.myCellRequestedToOpenAnswerVC(cell: self)
}
}
The last part happens in MyTableViewController - first, in your cellForRow method assign the view controller as delegate, something like this - cell.delegate = self, and make the view controller conform to MyCellDelegate:
extension MyTableViewController: MyCellDelegate {
func myCellRequestedToOpenAnswerVC(cell: MyCell) {
self.goToNextView()
}
}
Now, whenever the condition is met, your view controller will get informed about it and be able to act accordingly.
If you are not familiar with protocols and delegation pattern, I highly recommend reading through the docs, as it is something used extensively in CocoaTouch.
I want to update the label in the DetailViewController everytime I selected a tableRow in the MasterViewController. To achieve this, I designed a delegate, which I have in the MasterVC
protocol TestTableViewControllerDelegate {
func selectedRow(selectedCar : Car)
}
class TestTableViewController: UITableViewController {
...
var delegate : TestTableViewControllerDelegate?
override func viewDidLoad() {
super.viewDidLoad()
self.delegate = DetailViewController()
The delegate works just fine, (it is implemented correctly in the DetailVC), it can pass values from TestTableVC to DetailVC and also correctly do println(), which prints a new Car.model String to the console every time I select a row in the TTVC.
The DetailVC looks like this (shortened):
class DetailViewController: UIViewController, TestTableViewControllerDelegate {
#IBOutlet var textLabel: UILabel!
var theCar : Car? {
didSet(newCar) {
refreshUI()
}
}
override func viewDidLoad() {
super.viewDidLoad()
refreshUI()
}
func selectedRow(selectedCar : Car) {
theCar = selectedCar
refreshUI()
}
func refreshUI() {
textLabel?.text = theCar!.model
}
}
I can achieve any kind of action with my delegate, expect for refreshing the UI. I have tried numerous ways, this is my latest attempt. Before that, I tried setting the textLabel's text property directly within the delegate method, didn't work. This problem only occurs when working with the UI-elements. I know it has something to do with the view not being loaded yet, but why does my refreshUI() function not work at all?
I am still a beginner, so any tip or help would be much appreciated!
A workaround I've used is to cerate a properly in the delegate and pass the value to it instead of the UI element. When the view loads I update the label's text properly with the value of the delegates property. I would think there's a better way to do this (I'm new to programming) but this is the best soultion I've come up with so far. Will update with sample code soon.
I have been pulling my hair out trying to get this 'Delegate' thing to work in Swift for an App I am working on.
I have two files: CreateEvent.swift and ContactSelection.swift, where the former calls the latter.
CreateEvent's contents are:
class CreateEventViewController: UIViewController, ContactSelectionDelegate {
/...
var contactSelection: ContactSelectionViewController = ContactSelectionViewController()
override func viewDidLoad() {
super.viewDidLoad()
/...
contactSelection.delegate = self
}
func updateInvitedUsers() {
println("this finally worked")
}
func inviteButton(sender: AnyObject){
invitedLabel.text = "Invite"
invitedLabel.hidden = false
toContactSelection()
}
/...
func toContactSelection() {
let contactSelection = self.storyboard?.instantiateViewControllerWithIdentifier("ContactSelectionViewController") as ContactSelectionViewController
contactSelection.delegate = self
self.navigationController?.pushViewController(contactSelection, animated: true)
}
ContactSelection's contents are:
protocol ContactSelectionDelegate {
func updateInvitedUsers()
}
class ContactSelectionViewController: UITableViewController {
var delegate: ContactSelectionDelegate?
override func viewDidLoad() {
super.viewDidLoad()
self.delegate?.updateInvitedUsers()
}
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
// Stuff
self.delegate?.updateInvitedUsers()
}
}
What am I doing wrong? I am still new and don't fully understand this subject but after scouring the Internet I can't seem to find an answer. I use the Back button available in the Navigation Bar to return to my CreateEvent view.
var contactSelection: ContactSelectionViewController = ContactSelectionViewController()
This is instantiating a view controller directly, and the value never gets used. Since it looks like you're using storyboards, this isn't a good idea since none of the outlets will be connected and you'll get optional unwrapping crashes. You set the delegate of this view controller but that's irrelevant as it doesn't get used.
It also isn't a good idea because if you do multiple pushes you'll be reusing the same view controller and this will eventually lead to bugs as you'll have leftover state from previous uses which might give you unexpected outcomes. It's better to create a new view controller to push each time.
In your code you're making a brand new contactSelection from the storyboard and pushing it without setting the delegate.
You need to set the delegate on the instance that you're pushing onto the navigation stack.
It's also helpful to pass back a reference in the delegate method which can be used to extract values, rather than relying on a separate reference in the var like you're doing.
So, I'd do the following:
Remove the var contactSelection
Add the delegate before pushing the new contactSelection object
Change the delegate method signature to this:
protocol ContactSelectionDelegate {
func updateInvitedUsers(contactSelection:ContactSelectionViewController)
}
Change your delegate calls to this:
self.delegate?.updateInvitedUsers(self)