NSUnknownKeyException ? Why?

Question

I have tried in Xcode7 for many times, but still follow the problem as below:

TapWar[10487:391936] *** Terminating app due to uncaught exception 'NSUnknownKeyException', 
reason: '[<TapWar.ViewController 0x7f9848483220> setValue:forUndefinedKey:]: 
this class is not key value coding-compliant for the key buttomButtonAction.'

The codes are nothing special, just outlets and action for storyboards import UIKit

class ViewController: UIViewController {


    @IBOutlet weak var topButton: UIButton!
    @IBOutlet weak var buttomButton: UIButton!
    @IBOutlet weak var topLabel: UILabel!
    @IBOutlet weak var buttomLabel: UILabel!


    override func viewDidLoad() {
        super.viewDidLoad()
    score = 0

    topLabel.text = "\(score)"
    buttomLabel.text = "\(score)"

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
//Button on top to tap
    @IBAction func topButtonAction(sender: UIButton) 

    }
//Button under to tap
    @IBAction func buttomButtonAction(sender: AnyObject) {

    }
}

Answer 1

Did you check your IBOutlet or IBAction connection? That error usually cause name inconsistence.