Uncaught exception of type NSException

Question

I'm beginning to teach myself Swift, I am truly a beginner and I am working on a calculator app just as an intro project. I keep getting a thread error and it is terminating with an uncaught exception of type NSException. I've read in several places that this is usually caused by a missing or wrong connection from the storyboard to the view controller but I triple checked all of my connections and I don't think that is the problem. Here is my code for the view controller, is there an issue with it? I followed a tutorial for the most part.

import UIKit

extension String{
    var doubleValue: Double{
        if let number = NSNumberFormatter().numberFromString(self) {
            return number.doubleValue
        }
        return 0
    }
}

class ViewController: UIViewController {

var isTypingNumber = false
var firstNumber:Double? = 0
var secondNumber:Double? = 0
var operation = ""


@IBOutlet var calculatorDisplay: UILabel!
@IBAction func numberTapped(sender: AnyObject) {
    var number = sender.currentTitle

    if isTypingNumber {
        calculatorDisplay.text = calculatorDisplay.text! + number!!
    } else{
        calculatorDisplay.text = number
        isTypingNumber = true
    }
}
@IBAction func calculationTapped(sender: AnyObject) {
    isTypingNumber = false
    firstNumber = calculatorDisplay.text!.doubleValue
    operation = sender.currentTitle!!
}
@IBAction func equalsTapped(sender: AnyObject) {
    isTypingNumber = false
    var result = 0.0
    secondNumber = calculatorDisplay.text!.doubleValue

    if operation == "+"{
        result = firstNumber! + secondNumber!
    } else if operation == "-"{
        result = firstNumber! - secondNumber!
    } else if operation == "*"{
        result = firstNumber! * secondNumber!
    }
    else if operation == "/"{
        result = firstNumber! / secondNumber!
    }

    calculatorDisplay.text = "\(result)"
}



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.
}


}

I really appreciate any help I can get!

Answer 1

Did you happen to change the name of any IBOutlet or IBAction since first installing it into the Storyboard/xib?

Try going to your viewcontroller in Interface Builder, right-click the VC object to see all connected outlets, and check that everything's hooked up and that there aren't any dead links. (i.e. if you renamed func equalsTapped() to func equalsTapped(sender: AnyObject), the exception will be raised because equalsTapped no longer exists, instead equalsTapped: now does, and the connection is to the first.)