Swift Sliders - fatal error: unexpectedly found nil while unwrapping an Optional value (lldb)

Question

I'm new to Swift and I was making a basic app that changes the text of a lable with the text in an inputbox and I wanted to add RGB sliders to change the color of the lable that will be changed but I got an errors soon as I try to move a slider.

fatal error: unexpectedly found nil while unwrapping an Optional value (lldb)

@IBOutlet weak var OutputLabel: UILabel!
@IBOutlet weak var InputField: UITextField!

@IBOutlet weak var RedSlider: UISlider!
@IBOutlet weak var BlueSlider: UISlider!
@IBOutlet weak var GreenSlider: UISlider!

@IBOutlet weak var RedLabel: UILabel!
@IBOutlet weak var GreenLabel: UILabel!
@IBOutlet weak var BlueLabel: UILabel!


var RedColor : Float = 0
var GreenColor : Float = 0
var BlueColor : Float = 0

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}


@IBAction func ChangeBtn(_ sender: Any) {
    OutputLabel.text = InputField.text
}

@IBAction func RedSliderAction(_ sender: UISlider) {
    changeColor()
}

@IBAction func GreenSliderAction(_ sender: UISlider) {
    changeColor()
}

@IBAction func BlueSliderAction(_ sender: UISlider) {
    changeColor()
}


func changeOutputLableColor() {
    OutputLabel.textColor = UIColor(red: CGFloat(RedColor), green: CGFloat(GreenColor), blue: CGFloat(BlueColor), alpha: 1.0)
    changeLabelNumbers()
}

func changeColor() {
    RedColor = RedSlider.value
    GreenColor = GreenSlider.value
    BlueColor = BlueSlider.value
    changeOutputLableColor()
}

func changeLabelNumbers() {
    let RoundedRed = String(format: "%0.0f", (RedColor * 255))
    let RoundedGreen = String(format: "%0.0f", (GreenColor * 255))
    let RoundedBlue = String(format: "%0.0f", (BlueColor * 255))

    RedLabel.text = "\(RoundedRed)"
    GreenLabel.text = "\(RoundedGreen)"
    BlueLabel.text = "\(RoundedBlue)"
}

can someone help me figure it out?

Answer 1

You might have not connected the @IBOutlets RedSlider,BlueSlider and/or GreenSlider to the UISlider on the storyboard. That'll result in the error you are receiving.

Alternatively you might have not connected the @IBOutlets RedLabel, GreenLabel and/or BlueLabel. Just look for the line which your codes crash at and it'll hint you which one is not connected.