Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP,subcode = 0x0)

Question

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

    var userIsInTheMiddleOfTypingNumber: Bool = false

    @IBAction func appendDigit(sender: UIButton) {
        let digit = sender.currentTitle!

        if (userIsInTheMiddleOfTypingNumber) {
            label.text = label.text! + digit
        }
        else {
            label.text = digit
            userIsInTheMiddleOfTypingNumber = true
        }
    }
}

I am currently creating a calculator app. For some reason, when I run the simulator and try to input some digits in, the siumulator freezes, and the error of bad_instruction appears on the line:

label.text = digit

How would I fix this situation?

To learn how to debug a crash, please see http://www.raywenderlich.com/10209/my-app-crashed-now-what-part-1 — rmaddy, May 06 '16 at 16:46
If this is an "unexpectedly found nil" crash – then also see [this extensive Q&A](http://stackoverflow.com/questions/32170456/what-does-fatal-error-unexpectedly-found-nil-while-unwrapping-an-optional-valu) on the error. — Hamish, May 06 '16 at 16:48

score 1 · Answer 1 · answered May 06 '16 at 16:42

1

Looks like you forgot to connect the label in the Storyboard with the outlet.

answered May 06 '16 at 16:42

dasdom

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score 1 · Answer 2 · answered May 06 '16 at 16:43

Looks like the currentTitle property is nil which results in a crash. You are force unwrapping the property without any nil check.

@IBAction func appendDigit(sender: UIButton) {
    if let digit = sender.currentTitle {
        if (userIsInTheMiddleOfTypingNumber) {
            label.text = label.text! + digit
        }
        else {
            label.text = digit
            userIsInTheMiddleOfTypingNumber = true
        }
    }
}

OR

It could be the reason specified by @dasdom

Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP,subcode = 0x0)

2 Answers2