Getting error while setting alpha of UIView Swift

Question

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• What does “fatal error: unexpectedly found nil while unwrapping an Optional value” mean? 11 answers

I'm making quiz app and when I want to change value of alpha of my UIView I'm getting error fatal error: unexpectedly found nil while unwrapping an Optional value, before it warms fine but I'm remodeling my app and I think that I delete something or change by mistake. I don't want to put all my code here because it is quiet large so I will cut most important parts.

import UIKit

class ViewController: UIViewController{

@IBOutlet weak var questionLabel: UILabel!
@IBOutlet weak var answerStackView: UIStackView!

// Feedback screen
@IBOutlet weak var resultView: UIView!
@IBOutlet weak var dimView: UIView!
@IBOutlet weak var resultLabel: UILabel!
@IBOutlet weak var feedbackLabel: UILabel!
@IBOutlet weak var resultButton: UIButton!

@IBOutlet weak var resultViewBottomConstraint: NSLayoutConstraint!
@IBOutlet weak var resultViewTopConstraint: NSLayoutConstraint!

var currentQuestion:Question?

var  model:QuizModel?
var questions = [Question]()

var numberCorrect = 0

override func viewDidLoad() {
    super.viewDidLoad()
    model = QuizModel()
    model?.getQuestions()
}

override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
    super.init(nibName: nil, bundle: nil)
}

required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
}
func setAll(questionsReturned:[Question]) {

    self.loadViewIfNeeded()
    // Do any additional setup after loading the view, typically from a nib.

    // Hide feedback screen
    dimView.alpha = 0

    // Call get questions
    questions = questionsReturned

    // Check if there are questions
    if questions.count > 0 {

        currentQuestion = questions[0]

        // Load state
        loadState()

        // Display the current question
        displayCurrentQuestion()
    }

print("Called!")

}


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

func displayCurrentQuestion() {

    if let actualCurrentQuestion = currentQuestion {

        // Set question label to alpha 0
        questionLabel.alpha = 0

        // Set the question label
        questionLabel.text = actualCurrentQuestion.questionText

        UIView.animate(withDuration: 1, delay: 0, options: .curveEaseOut, animations: { 

                self.questionLabel.alpha = 1

            }, completion: nil)

        // Create the answer buttons and place them into the scrollview
        createAnswerButtons()

        // Save state
        saveState()
    }

}

im getting error while setting alpha of dimView and questionLabel. I don't know why because they are connected by the storyboard

PS. When I set breakpoint on this dimView.alpha = 0 and type po dimview in console it says that dimView is nil

Edit: I have some informations that can be useful. When I set alpha of DimView and questionLabel before I call model?.getQuestions() it works and when I set breakpoint there and type po dimView! into console it returns some values.

And questionsLabel have something too.

But when code goes into model?.getQuestions(), and then I type po dimView! it returns nil.

Answer 1

setAll(questionsReturned:[Question]) is getting called before viewDidLoad() is called. The @IBOutlets aren't connected until just before viewDidLoad() is called.

class ViewController: UIViewController {
    @IBOutlet weak var myLabel: UILabel!

    var myText: String = ""

    func viewDidLoad() {
        super.viewDidLoad()
        myLabel.text = myText
    }

    set(myText: String) {
        self.myText = myText
    }
}

Do it like the above...

-- Edit --

I notice in your screenshots that displayCurrentQuestion is being called on a different view controller object than the view controller that was loaded in the screenshot where viewDidLoad is called. It could be that you are creating a second view controller somewhere?

Do this... Put break points at the beginning of your displayCurrentQuestion and viewDidLoad methods. Then run your app. You will find that either displayCurrentQuestion is getting called before viewDidLoad is, or it is being called on a different object that viewDidLoad was called on (you can tell it's a different object by the hex value of the self variable.)

Answer 2

It is also good to check your IBOutlet connections with your viewcontroller in storyboard, there might be wrong connections