如何调用UIBarButtonItem上的函数？

Question

我有一个UIPickerView，我在UIBarButtonItems中添加UIToolBar。当我按下按钮 «完成»，请勿调用«donePress»功能。怎么称呼它？

class SearchViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource, UITextFieldDelegate {


    @IBOutlet weak var Picker: UIPickerView! = UIPickerView()

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override func viewDidLoad() {
       super.viewDidLoad()
       Picker.delegate = self
       Picker.dataSource = self
       self.setToolBar()
}

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func setToolBar() {
            let toolbar : UIToolbar = UIToolbar()
            toolbar.tag = 10
            toolbar.sizeToFit()
            toolbar.barStyle = UIBarStyle.BlackTranslucent
            toolbar.tintColor = UIColor.orangeColor()
            toolbar.translucent = true


            let doneButton = UIBarButtonItem(title: "Done", style: UIBarButtonItemStyle.Plain, target: self, action: "donePress")
            let spaceButton = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.FlexibleSpace, target: nil, action: nil)
            let cancelButton = UIBarButtonItem(title: "Cancel", style: UIBarButtonItemStyle.Plain, target: self, action: "donePress")

            toolbar.setItems([cancelButton, spaceButton, doneButton], animated: false)
            toolbar.userInteractionEnabled = true            
            self.Picker.addSubview(toolbar)

}

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       func donePress() {
        print(«say Hello!»)
    }