Swift textfield keyboard 에 Done 버튼 생성하기

import Foundation
import UIKit

extension UITextField{
    @IBInspectable var doneAccessory: Bool {
        get {
            return self.doneAccessory
        }
        set (hasDone) {
            if hasDone {
                addDoneButtonOnKeyboard()
            }
        }
    }
    
    func addDoneButtonOnKeyboard(){
        let doneToolbar: UIToolbar = UIToolbar(frame: CGRect(x:0,y:0,width: UIScreen.main.bounds.width,height: 50))
        doneToolbar.barStyle = .default
        doneToolbar.tintColor = .green
        
        let flexSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
        let done: UIBarButtonItem = UIBarButtonItem(title: "키워드 등록", style: .done, target: self, action: #selector(doneButtonAction))
        
        let items = [flexSpace,done]
        doneToolbar.items = items
        doneToolbar.sizeToFit()
        
        self.inputAccessoryView = doneToolbar
    }
    
    @objc func doneButtonAction() {
        self.resignFirstResponder()
    }
}