This question already has answers here:
What does "Fatal error: Unexpectedly found nil while unwrapping an Optional value" mean?
(16 answers)
iOS - Push viewController from code and storyboard
(5 answers)
Closed 4 years ago.
I'm trying to show one of my ViewControllers of a different storyboard programmatically. But for some reasons the properties of the ViewController I'm trying to show are nil.
That's my error: Unexpectedly found nil while unwrapping an Optional value
I'm getting the error in my SecondViewController. It is showing but
my app crashes due to the properties being nil.
That's my code:
let secondStoryBoard = UIStoryboard(name: "SecondStoryBoard", bundle: nil)
let secondViewController = secondStoryBoard.instantiateViewController(withIdentifier: "secondVC") as! SecondVC
self.navigationController?.pushViewController(secondViewController, animated: true)
That's the code producing the error:
class SecondVC: ViewController
{
#IBOutlet weak var mapView: MKMapView!
mapView.isHidden = true // ERROR!! Unexpectedly found nil while unwrapping an Optional value
}
SOLVED: just had to reconnect my #IBOutlet connections
This means that the following line is either nil or not of type SecondVC.
secondStoryBoard.instantiateViewController(withIdentifier: "secondVC")
I would verify in your storyboard that you have an identifier secondVC and that view controller is of type SecondVC.
Edit:
Based on the new code the OP posted in the question, changing the SecondVC to the following should work.
class SecondVC: ViewController
{
#IBOutlet weak var mapView: MKMapView!
override func viewDidLoad() {
mapView.isHidden = true
}
}
Basically this will wait until the view has loaded before accessing the mapView. For the original code, you were trying to access mapView before it has actually been loaded.
Edit 2:
It looks like mapView outlet is not properly linked to the storyboard.
Related
This question already has answers here:
What does "Fatal error: Unexpectedly found nil while unwrapping an Optional value" mean?
(16 answers)
Closed 2 years ago.
My Swift program is crashing with a fatal error, saying that "Unexpectedly found nil while implicitly unwrapping an Optional value" even with the GUARD statement . Can anyone help to tell me why, and how do I fix it? The code as follows:
var page: Page? {
didSet{
guard let unwrappedPage = page else { return }
NameLabel.text = unwrappedPage.dishName
Image.image = UIImage(named: unwrappedPage.imageName)
contentText.text = unwrappedPage.ingredient
contentText.text = unwrappedPage.instruction
}
}
The issue is likely that the outlets have not been hooked up by the time you set page, and if these outlets are implicitly unwrapped optionals (with the ! after the type name, e.g. UILabel!), that will result in the error you describe. This problem will manifest itself if, for example, you set page before the view controller in question has been presented and all of the outlets have been hooked up.
So, I’d recommend:
Use optional chaining with your #IBOutlet references so it won’t fail if the outlets haven’t been hooked up yet.
Go ahead and keep your didSet observer on page, if you want, but make sure you also update the controls in viewDidLoad in case page was set before the outlets were hooked up.
For example:
#IBOutlet weak var nameLabel: UILabel!
#IBOutlet weak var imageView: UILabel!
#IBOutlet weak var ingredientLabel: UILabel!
#IBOutlet weak var instructionLabel: UILabel!
var page: Page? { didSet { updateControls(for: page) } }
override func viewDidLoad() {
super.viewDidLoad()
updateControls(for: page)
}
func updateControls(for page: Page?) {
nameLabel?.text = page?.dishName
imageView?.image = page.flatMap { UIImage(named: $0) }
ingredientLabel?.text = page?.ingredient
instructionLabel?.text = page?.instruction
}
Note, you only need this didSet observer if the page might be set (again) after the view has been presented. If not, the didSet observer is not needed.
When I set the ViewController is the root navigation controller in the file Appdelegate.swift, like this:
var viewcontroller=ViewController();
var rootnavigationcontroller=UINavigationController.init(rootViewController: viewcontroller);
self.window?.rootViewController=rootnavigationcontroller;
Then I configure the ViewController like this:
class ViewController: UIViewController,CLLocationManagerDelegate,MKMapViewDelegate{
#IBOutlet weak var MapView: MKMapView!
override func viewDidLoad() {
super.viewDidLoad()
loadLaunchScreen();
Initilize();//Here configure the MapView parameters;
}
Then in the function Initilize(); I receive the error that means the MapView has found nil.
But if I do not set this Viewcontroller as the rootnavigationcontroller in the Appdelegate.swift, I will run well.
I want to ask why and how to solve it?
if you are using storyboards then try this
let stroyboard = UIStoryboard.init(name: "storyboardname", bundle: nil)//nil if its not out of your project
let ViewController = storyboard.instantiateViewController(withIdentifier: "yourstoryboadid")
var rootnavigationcontroller=UINavigationController.init(rootViewController: viewcontroller);
self.window?.rootViewController=rootnavigationcontroller;
above problem can happen when you use storybords and you are instantiate the viewController not from storyboard thats when your outlet found nil because is is not bounded to the outlet
if you are not using storyboards then your code is perfet
If you are not adding rootnavigationcontroller then your ViewController code will not be executed. So you will not get any error. For successfully MapView implementation, bind your MapView #IBOutlet in storyboard or XIB.
I am working on a project with Swift and Storyboards. It's a conversion project from a traditional IB and Objective-C project. I am having an issue with a UITableView instantiating when the view is loaded. Let me explain.
The project is a navigation project. Here is an overview of the Storyboard.
The Storyboard's first viewController is HomeViewController and is a landing page that displays general info. The next VC is called FeedViewController shows a number of RSS feeds. You can see an expanded screen shot of the NavigationController, HomeViewController and FeedViewController in the picture below.
My problem is that I can't get the tableView to Instantiate. I first checked to make sure that my tableView was connected as an outlet and that the dataSource and delegate properties were connected. You can see this in the pic below.
In my FeedViewController class I have an Outler property called feedsTableView. You can see the declaration in the code below.
class FeedViewController: UIViewController, UITableViewDataSource, UITableViewDelegate, FLODataHandlerDelegate
{
// View Contoller and Protocol Properties
var floView : FLOViewController?
var dataHandler : FLODataHandler?
// Interface and Content Properties
var refreshControl : UIRefreshControl?
// IBOutlets
#IBOutlet weak var feedsTableView: UITableView!
#IBOutlet weak var backgroundImage: UIImageView!
In the HomeViewController I have a FeedViewController property that I intend to use to gain access to FeedViewController's feedsTableView.
class HomeViewController: UIViewController, FLODataHandlerDelegate, MFMailComposeViewControllerDelegate
{
// View Contoller and Protocol Properties
var feedViewController : FeedViewController?
var dataHandler : FLODataHandler?
When HomeViewController's viewDidLoad() method is called I start the dataHandler - which instantiates the FeedViewController - and set it to my FeedViewController property.
override func viewDidLoad()
{
super.viewDidLoad()
// Set up the gesture recognizer to allow for swiping to the feed VC.
let recognizer = UISwipeGestureRecognizer(target: self, action: Selector("goToNext"))
recognizer.direction = UISwipeGestureRecognizerDirection.Left
self.view.addGestureRecognizer(recognizer)
// Start the data handler
self.setUpDataHandler()
}
setUpDataHandler()
func setUpDataHandler()
{
// Intitalize FeedVC for use later in the VC
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier("FeedViewController") as! FeedViewController
self.feedViewController = vc
}
I also have a fail safe that if someone were to go to the FeedViewController before the setUpDataHandler() method is called then I instantiate FeedViewController here as well.
func goToNext()
{
// Grab the feedViewController so it can be pushed onto the stack. Make sure you set up the storyboard identifier.
let feedVC = self.storyboard!.instantiateViewControllerWithIdentifier("FeedViewController") as! FeedViewController
self.feedViewController = feedVC
self.navigationController!.pushViewController(self.feedViewController!, animated: true)
}
However the feedsTableView is not getting instantiated. In the viewDidLoad() method of FeedViewController I attempt to add the feedsTableView to a UIRefreshController.
override func viewDidLoad()
{
super.viewDidLoad()
self.refreshControl = UIRefreshControl()
self.refreshControl!.addTarget(self, action: "refreshInvoked:state:", forControlEvents: UIControlEvents.ValueChanged)
// See the note in viewDidLoad in FLOViewController.
self.feedsTableView.addSubview(self.refreshControl!)
}
When the app runs I get the following error.
fatal error: unexpectedly found nil while unwrapping an Optional value
The image below shows were this is called. It's the viewDidLoad() of the FeedViewController. As you can see in the picture I even tried instantiating the feedsTableView before adding it to the UIRefreshController and I still get the error.
Any help would be greatly appreciated.
Take care,
Jon
The reason why it doesn't work in the very last case, where you manually instantiate UITableView and assign that to self.feedsTableView, is that self.feedsTableView is declared weak. Thus, the table view comes into existence, is assigned, and vanishes in a puff of smoke because it has no memory management. By the time you get to the last line, self.feedsTableView is nil once again.
Thus, the solution for that last case is to remove the weak designation from your feedsTableView declaration.
That will get you past the crash in that last case. But of course you won't see anything because you are not also inserting the table view into your interface.
I created file ViewController.swift
Here is the content of it
import Cocoa
public class ViewController: NSObject {
#IBOutlet var textView: NSTextView!
func InsertText(string:String) {
textView.insertText(string)
}
}
Then I bind textView to my NSTextView in my xib
and
now I want to insert text from AppDelegate via Controller
I do
let controller = ViewController()
controller.InsertText("Hello")
and it throw an error
fatal error: unexpectedly found nil while unwrapping an Optional value
which means that textView in nil, but why it is nil and how do I insert text using another class. if I do the same just in AppDelegate it works.
Instead of let controller = ViewController() ctrl-drag the view into your AppDelegate, name it reasonable and use that.
Why am I getting a 'nil' error/UILabel during my second pass thru the table cell listing iteration?
1) Inside cell
2) Inside cell
fatal error: unexpectedly found nil while unwrapping an Optional value
(lldb) po cell?.contentView.viewWithTag(TitleLabelTag)
nil
Here I link the elements in the code; and register the cell:
class DiaryTableViewCell: UITableViewCell {
#IBOutlet weak var TitleLabel: UILabel!
#IBOutlet weak var SubTitleLabel: UILabel!
#IBOutlet weak var leftImageView: UIImageView!
#IBOutlet weak var rightImageView: UIImageView!
}
class DiaryTableViewController: UITableViewController {
let kCellIdentifier = "DiaryCell"
var cellNib:UINib?
var diaryCell:DiaryTableViewCell?
var objects = NSMutableArray() //...global var.
override func viewDidLoad() {
self.title = "My Diary"
cellNib = UINib(nibName: "TableViewCells", bundle: nil)
tableView.registerClass(DiaryTableViewCell.self, forCellReuseIdentifier: kCellIdentifier)
}
...
Yet I'm getting the runtime error here:
Here's what I get in the console:
1) Inside cell
fatal error: unexpectedly found nil while unwrapping an Optional value
(lldb) po cell!.TitleLabel
nil
What's missing here?
It's a pretty bad idea to select a view with a tag. It's a much better idea to subclass your UITableViewCell and give it a property to access the elements.
If you are creating static cells and loading you need to create an IBoutlet for them in your .h correctly.
Moreover remove line
tableView.registerClass(...) statement from your code. Look at this link might help and is very similar except its for collectionview. -
Why is UICollectionViewCell's outlet nil?
1) I moved the cell registration to the viewDidLoad().
2) I forgot to place the '?' after the TitleLabel & SubTitleLabel; to notify the compiler that these labels could be nil.
I don't see the altered cell yet (empty rows); but I'm not getting runtime errors.
Unfortunately I merely cured the symptom; not the cause. I'm still getting nil UILabels.
...working on revision and cleaner code.