fatal error: unexpectedly found nil while unwrapping an Optional value while trying to change UILabel text

Question

I'm making a simple temperature converter for a mobile apps class using Swift. We're sort of breezing over swift so I don't have a lot of experience with it. I had a lot of problems getting it to compile but I eventually got everything all nice and neat, no warning or errors of any sort, and I'm happy with my MVC style code. The only problem is that when I enter a temp and click the Convert button, my log checkpoints prove that I'm getting he correct double value for conversion, and I caste it as a String, but when I try to change the outputText label I get the fatal error: unexpectedly found nil while unwrapping an Optional value. I was hoping it's something very simple that a second pair of eyes could catch. My app looks like this...

My ViewController is...

import UIKit

class ViewController: UIViewController
{

    @IBOutlet weak var tempInput: UITextField!
    @IBOutlet weak var tempOutput: UILabel!
    @IBOutlet weak var convertMethod: UISwitch!

    override func viewDidLoad()
    {
        print("view load confirmed");
        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 convert(sender: AnyObject!)
    {
        print ("button press confirmed");

        let t = Double(tempInput.text!)
        let m = convertMethod.on
        let result = convertModel(temp:t!,method:m)
        print("result has been set to object variable created as stated above");

        let afterConvert = result.convertTemp()
        print("the convertTemp method was called and the result was stored as the double: \(afterConvert)");

        let finalForm = String(afterConvert)
        print("converted the double into the string: \(finalForm)");

        tempOutput.text = finalForm
        //^^^^^^^ this is the line that fails
    }
}

and my convertModel class (i know, the class should be capitalized, by the time I noticed and tried to change it, it broke everything) is...

import Foundation
class convertModel
{
    var temp:Double?
    var method:Bool?

    init(temp:Double,method:Bool)
    {
        self.temp = temp
        self.method = method
        print("object of type convertModel created with \(temp) as temp and \(method) as method");
    }

    func convertTemp()->Double
    {
        print("convertTemp method entered");

        if method == true
        {
            print("if conditional entered");
            print("conversion completed, exiting convertTemp method");

            return (temp! * (9/5) + 32)
        }
        else
        {
            print("else conditional entered");
            print("conversion completed, exiting convertTemp method");
            return (temp! - 32) * (5/9)
        }
    }
}

Any help is greatly appreciated. But please bear in mind that this is very Swift 101, so any overly complicated solutions don't help greatly. Thanks.

Answer 1

So I don't know why or how UILabel lost it's initial link with the ViewController, but in an act of desperation I did the old Ctrl + Click drag over to ViewController and just named the resulting Outlet something else(tempOutputs), renamed the text assignment and now it works. So this isn't so much an answer as it is a work around for anyone who ends up here as well.