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)
    }
  }
}