Loadingbar component for WKWebView

example.swift

import UIKit
import WebKit
import LoadingBarKit

class ViewController: UIViewController {
  @IBOutlet var loadingBar: LoadingBar!
  var webView: WKWebView?
  override func viewDidLoad() {
    super.viewDidLoad()
      self.webView?.addObserver(self, forKeyPath: "estimatedProgress", options: NSKeyValueObservingOptions.New, context: nil)
    }
  }
  
  deinit {
    self.webView?.removeObserver(self, forKeyPath: "estimatedProgress")
  }
  
  // MARK: - Progress monitoring (KVO)
  override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject, change: [NSObject : AnyObject], context: UnsafeMutablePointer<Void>) {
    if (keyPath == "estimatedProgress" && object as NSObject == self.webView!) {
      self.loadingBar.progress = Float(self.webView!.estimatedProgress)
    }
  }
}

loadingBar.swift

//
//  LoadingBar.swift
//

import UIKit

@IBDesignable
public class LoadingBar: UIView {
  @IBInspectable public var progress: Float = 0.0 {
    didSet {
      UIView.animateWithDuration(0.1, animations: { () -> Void in
        var width = self.frame.size.width * CGFloat(self.progress)
        self.innerBar?.frame = CGRect(x: CGFloat(0.0), y: CGFloat(0.0), width: width, height: self.frame.size.height)
        if self.progress >= 1.0 {
          self.alpha = 0.0
        } else {
          self.alpha = 1.0
        }
      })
    }
  }
  @IBInspectable var color: UIColor? {
    didSet {
      self.innerBar?.backgroundColor = self.color!
    }
  }
  var innerBar: UIView?
    
  override public func layoutSubviews() {
    super.layoutSubviews()
        
    self.userInteractionEnabled = false
    self.backgroundColor = UIColor.clearColor()
    if self.color == nil {
      self.color = self.tintColor
    }
        
    if innerBar == nil {
      var width = self.frame.size.width * CGFloat(self.progress)
      self.innerBar = UIView(frame: CGRect(x: CGFloat(0.0), y: CGFloat(0.0), width: width, height: self.frame.size.height))
      self.innerBar?.backgroundColor = self.color
      self.addSubview(self.innerBar!)
    }
  }
}

Any idea implementing this in swift 3
self.webView?.addObserver(self, forKeyPath: "estimatedProgress", options: NSKeyValueObservingOptions.New, context: nil)

need to be
self.webView?.addObserver(self, forKeyPath: "estimatedProgress", options: NSKeyValueObservingOptions.new, context: nil)
Just the .new insted of .New

But i am not able to observe the estimatedProgress value. Let me know if you have any ideas