(UILabel) nil, Cannot insert text in the label - ios

Question

Good day,
I seem to have such a simple problem but I just can not wrap my head around it.
I have a container view inside a view controller. In that container I have few labels. The container has its own view controller. In the view controller for the container I have a timer running and I want that label to show the timer. But every time I use that label the app crashes with
"Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value"
If I comment the line out that has this label then everything runs fine.
#IBOutlet weak var timeLabel: UILabel!
var counter = 0.0
var timer = Timer()
var isRunning = false
func startStopTimer () {
if isRunning {
timer.invalidate()
isRunning = false
}else {
timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(updateTimer), userInfo: nil, repeats: true)
isRunning = true
}
}
#objc func updateTimer() {
counter = counter + 0.1
timeLabel.text = String(counter)
}
This is the first time I play around with container view in the Main storyboard.
Anyone that knows what I am doing wrong or has suggestion what I can try to change?
Thanks
Jonas
Full Code
class MainViewController: UIViewController {
#IBOutlet weak var topContainer: UIView!
#IBOutlet weak var informationContainer: UIView!
#IBOutlet weak var startStopButtonOutlet: UIButton!
let informationContainerVC = InformationContainerViewController()
override func viewDidLoad() {
super.viewDidLoad()
setupView()
}
func setupView() {
topContainer.layer.cornerRadius = 5
topContainer.layer.masksToBounds = true
informationContainer.layer.cornerRadius = 5
informationContainer.layer.masksToBounds = true
startStopButtonOutlet.layer.cornerRadius = 5
startStopButtonOutlet.layer.masksToBounds = true
}
#IBAction func startStopButton_TouchUpInside(_ sender: UIButton) {
informationContainerVC.startStopTimer()
UIButton.animate(withDuration: 0.1, delay: 0.0, options: [.allowUserInteraction, .curveEaseOut], animations: {
sender.transform = CGAffineTransform.identity
}, completion: nil)
if informationContainerVC.isRunning {
startStopButtonOutlet.setTitle("Push to Pause", for: .normal)
}else {
startStopButtonOutlet.setTitle("Push to Start", for: .normal)
}
}
#IBAction func startStopButton_TouchDown(_ sender: UIButton) {
UIButton.animate(withDuration: 0.1, delay: 0.0, options: [.allowUserInteraction, .curveEaseIn], animations: {
sender.transform = CGAffineTransform(scaleX: 0.9, y: 0.9)
if self.informationContainerVC.isRunning {
sender.backgroundColor = UIColor.white.withAlphaComponent(0.5)
}else {
sender.backgroundColor = UIColor.green.withAlphaComponent(0.8)
}
}, completion: nil)
}
#IBAction func startStopButton_TouchUpOutside(_ sender: UIButton) {
UIButton.animate(withDuration: 0.1, delay: 0.0, options: [.allowUserInteraction, .curveEaseOut], animations: {
sender.transform = CGAffineTransform.identity
}, completion: nil)
}
}
Here is the code for the container view controller
class InformationContainerViewController: UIViewController {
#IBOutlet weak var timeLabel: UILabel!
var counter = 0.0
var timer = Timer()
var isRunning = false
func startStopTimer () {
if isRunning {
timer.invalidate()
isRunning = false
}else {
timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(updateTimer), userInfo: nil, repeats: true)
isRunning = true
}
}
#objc func updateTimer() {
counter = counter + 0.1
timeLabel.text = String(counter)
}
}

Answer 1

When you say let informationContainerVC = InformationContainerViewController() you are creating a new instance of InformationContainerViewController that is not linked to the storyboard, so none of the outlets are set.
You need to get a reference to the view controller instance that is actually in your container view. You can do this in prepare(for segue:); If you look at your storyboard you will see that there is an embed segue that links your containing view controller to the contained view controller.
In your MainViewController:
var informationContainerVC: InformationContainerViewController?
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destVC = segue.destination as? InformationContainerViewController {
self.informationContainerVC = destVC
}
}
#IBAction func startStopButton_TouchUpInside(_ sender: UIButton) {
informationContainerVC?.startStopTimer()
UIButton.animate(withDuration: 0.1, delay: 0.0, options: [.allowUserInteraction, .curveEaseOut], animations: {
sender.transform = CGAffineTransform.identity
}, completion: nil)
if informationContainerVC?.isRunning {
startStopButtonOutlet.setTitle("Push to Pause", for: .normal)
} else {
startStopButtonOutlet.setTitle("Push to Start", for: .normal)
}
}
Now you will have a reference to the correct view controller instance