Swift2 NSUnknownKeyException？为什么？

我已经在Xcode7中尝试了很多次，但仍然存在以下问题：

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.'

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您是否检查了IBOutlet或IBAction连接？

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该错误通常会导致名称不一致。

检查IBOutlet，确保其连接正确！

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) {

    }
}