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.
in this issue i tried to unwrap it by adding ! next verifiedLabel in viewDidLoad to become verifiedLabel!.text but the result is still printing Fatal error: Unexpectedly found nil while unwrapping an Optional value. Thank you
override func viewDidLoad() {
super.viewDidLoad()
verifiedLabel.text = "" }
self.verifiedLabel.text = user.isPhoneVerified ? "Verified" : "Not Verified" }
You are force unwrapping an optional by adding a !, so if the value is null like it is in your case the program will crash.
To unwrap an optional in a safe way (for a generic case) follow this method from Hacking With Swift:
var name: String? = nil
if let unwrapped = name {
print("\(unwrapped.count) letters")
} else {
print("Missing name.")
}
In your SPECIFIC case however verifiedLabel is likely your label set on a storyboard. So you can unwrap it like var verifiedLabel:UILabel! since the value should NOT be null.
So now since its null, a) please check your outlet connections and if everything looks good b) check this thread for debugging: IBOutlet is nil, but it is connected in storyboard, Swift
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 problem is that I want to set the value of a slider to a UserDefault. In the first version of the app everything worked fine and I use the same code in version 2. Now Xcode shows the error "Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value", but I never have used Optionals in the code. I have updated Xcode, maybe there is a problem.
Thank you in advance
func speichernNutzerEinstellungenIntervall(){
standard.set(zeitInsgesamt, forKey: Keys.speichernZeitInsgesamt)
}
func überprüfenLängeIntervall(){
let speichernZeitInsgesamt = standard.integer(forKey: Keys.speichernZeitInsgesamt)
zeitInsgesamt = speichernZeitInsgesamt
sliderIntervallOutlet.setValue(Float(zeitInsgesamt), animated: true) //Here I get the error}
(I have declared the variable "zeitInsgesamt" as a global variable. Don't know if this is important.)
The value of sliderIntervallOutlet is nil. Try to check nil value for property before set any value. Like this
func überprüfenLängeIntervall(){
let speichernZeitInsgesamt = standard.integer(forKey: Keys.speichernZeitInsgesamt)
zeitInsgesamt = speichernZeitInsgesamt
if sliderIntervallOutlet != nil {
sliderIntervallOutlet.setValue(Float(zeitInsgesamt), animated: true)
}
}
This question already has answers here:
What does "Fatal error: Unexpectedly found nil while unwrapping an Optional value" mean?
(16 answers)
Closed 6 years ago.
Hi all I'm creating a chat app, using firebase.
when I get to the screen to create a channel it crashes saying found nil while unwrapping optional value. If i go back into the app the channel has been created so i presume it is finding nil when changing viewcontrolers and there must be nothing in the database for the new channel under messages. below is the code and where it crashes.
var channelRef: FIRDatabaseReference?
private lazy var messageRef: FIRDatabaseReference = self.channelRef!.child("messages")
then it crashes here...
private func observeMessages() {
messageRef = channelRef!.child("messages")
this function is called on view did load
Instead of force unwraps you should use and if let like this:
if let channelRef = channelRef {
messageRef = channelRef.child("messages")
} //maybe add an else and do some logic if value is not there
Or you could declare var channelRef: FIRDatabaseReference! if you expect it to always be there and be of this type
This question already has answers here:
What does "Fatal error: Unexpectedly found nil while unwrapping an Optional value" mean?
(16 answers)
Closed 1 year ago.
I have a code I am writing and its going well but I am having trouble with UISliders...specifically...setting values. I have used the sliders and now I want to reset them to the original state (0 to 10 with a value of 0 and the slider all the way to the left. I have...
#IBOutlet weak var redHorizontalSlider: UISlider!
Inside viewDidLoad:
redHorizontalSlider!.minimumValue = 0.0
redHorizontalSlider!.maximumValue = 1.0
redHorizontalSlider!.setValue(0.0, animated: false)
and when I print the values its giving me a nil and an error:
Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value
I have played around with ! and ? in the declaration of the Object and the calls but to no avail.
This error is going to happen because the value of your slider is nil. Check your connections to make sure that your storyboard slider is connected to the slider variable.
This question already has answers here:
What does "Fatal error: Unexpectedly found nil while unwrapping an Optional value" mean?
(16 answers)
Fatal error: unexpectedly found nil while unwrapping an Optional values [duplicate]
(13 answers)
Closed 6 years ago.
This code is causing my application to crash and I can't figure out a way to fix it. The error is : fatal error: unexpectedly found nil while unwrapping an Optional value
Any idea how I can fix it? The two lines I'm returning in my createCharacters() function is whats causing the crash:
class NACharacters {
var featuredImage : UIImage!
init(featuredImage: UIImage){
self.featuredImage = featuredImage
}
static func createCharacters() -> [NACharacters]{
return[
//THE TWO LINES BELOW CAUSE THE CRASH
NACharacters(featuredImage: UIImage(named: "Diplo Squad")!),
NACharacters(featuredImage: UIImage(named: "StopIcon")!)
]
}
}
Solution: I simply needed to delete the space between "Diplo" and "Squad". It seems this was returning nil.
check if your images "Diplo Squad" und "StopIcon" exist.
(You may need to remove the space in the first image name)
At least one of these UIImage(name: "...") calls returns nil and that's probably the crash reason.
The only thing that could be nil lines are in the UIImages. check that they exist in your projectNavigator or assets.
I am working on a new project in Swift and am having a tough time understand a particular use of optionals. I have declared a UIRefreshControl property for use in the class. I declared it as an optional.
var refreshControl : UIRefreshControl?
In the viewDidLoad() I first tried the following.
override func viewDidLoad()
{
super.viewDidLoad()
self.refreshControl!.addTarget(self, action: Selector("refreshInvoked:"), forControlEvents: UIControlEvents.ValueChanged)
self.feedsTableView.addSubview(self.refreshControl!)
}
The app crashed on
self.refreshControl!.addTarget(self, action: Selector("refreshInvoked:"), forControlEvents: UIControlEvents.ValueChanged
telling me the following. "fatal error: unexpectedly found nil while unwrapping an Optional value."
I realized that I had not instantiated the UIRefreshControl object so I tried the following to fix it.
override func viewDidLoad()
{
super.viewDidLoad()
self.refreshControl! = UIRefreshControl()
self.refreshControl!.addTarget(self, action: Selector("refreshInvoked:"), forControlEvents: UIControlEvents.ValueChanged)
self.feedsTableView.addSubview(self.refreshControl!)
}
To my surprise I received the same error message for
self.refreshControl! = UIRefreshControl()
When I remove the ! the error goes away and everything works.
self.refreshControl = UIRefreshControl()
Questions
Why don't we have to forcibly unwrap the optional when we instantiate it?
Would I be better off declaring the property as an implicitly unwrapped optional? If so why?
var refreshControl : UIRefreshControl!
Unwrapping is an action that is done on an optional variable to extract the value stored in it, if not nil. The opposite action is wrapping, done when a value is stored in an optional variable - which doesn't need any special operator to be performed. If you use forced unwrapping to assign, you are actually unwrapping a value from an optional variable, which is nil, causing the exception to be thrown
It makes sense declaring a property as implicitly unwrapped if these conditions are met:
a. the property is supposed to be non-nil for the entire lifecycle of the container instance
b. the property cannot be initialized in the constructor
This is the case of all outlets, which are defined as implicitly unwrapped because their initialization is done at a later stage in the view controller life cycle. I usually avoid implicitly unwrapped optionals, that's one of the few cases where I tolerate them.
Well...
? (Optional) indicates your variable may contain a nil value while ! (unwrapper) indicates your variable must have a memory (or value) when it is used (tried to get a value from it) at runtime.
The main difference is that optional chaining fails gracefully when the optional is nil, whereas forced unwrapping triggers a runtime error when the optional is nil.
To reflect the fact that optional chaining can be called on a nil value, the result of an optional chaining call is always an optional value, even if the property, method, or subscript you are querying returns a nonoptional value. You can use this optional return value to check whether the optional chaining call was successful (the returned optional contains a value), or did not succeed due to a nil value in the chain (the returned optional value is nil).
Specifically, the result of an optional chaining call is of the same type as the expected return value, but wrapped in an optional. A property that normally returns an Int will return an Int? when accessed through optional chaining.
var defaultNil : Int? // declared variable with default nil value
println(defaultNil) >> nil
var canBeNil : Int? = 4
println(canBeNil) >> optional(4)
canBeNil = nil
println(canBeNil) >> nil
println(canBeNil!) >> // Here nil optional variable is being unwrapped using ! mark (symbol), that will show runtime error. Because a nil optional is being tried to get value using unwrapper
var canNotBeNil : Int! = 4
print(canNotBeNil) >> 4
var cantBeNil : Int = 4
cantBeNil = nil // can't do this as it's not optional and show a compile time error
Here is basic tutorial in detail, by Apple Developer Committee.