Updated for Swift 5 compatibility

KeyboardBoundView.swift

//
//  KeyboardBoundView.swift
//  Mechawrench
//
//  Created by Mechawrench on 4/17/19.
//  Copyright © 2019 Mechawrench. All rights reserved.
//
import UIKit

extension UIView {
    
    func bindToKeyboard(){
        NotificationCenter.default.addObserver(self, selector: #selector(UIView.keyboardWillChange(_:)), name: UIResponder.keyboardWillChangeFrameNotification, object: nil)
    }
    
    @objc func keyboardWillChange(_ notification: NSNotification) {
        let duration = notification.userInfo![UIResponder.keyboardAnimationDurationUserInfoKey] as! Double
        let curve = notification.userInfo![UIResponder.keyboardAnimationCurveUserInfoKey] as! UInt
        let curFrame = (notification.userInfo![UIResponder.keyboardFrameBeginUserInfoKey] as! NSValue).cgRectValue
        let targetFrame = (notification.userInfo![UIResponder.keyboardFrameEndUserInfoKey] as! NSValue).cgRectValue
        let deltaY = targetFrame.origin.y - curFrame.origin.y
        
        UIView.animateKeyframes(withDuration: duration, delay: 0.0, options: UIView.KeyframeAnimationOptions(rawValue: curve), animations: {
            self.frame.origin.y += deltaY
            
        },completion: {(true) in
            self.layoutIfNeeded()
        })
    }
}