WKWebView controller example with progress bar

MyWKWebVC.Swift

//
//  MyWKWebVC.Swift
//  Example
//
//  Created by Fahied on 04/01/2017.
//

import Foundation
import UIKit
import WebKit

var myContext = 0

class MyWKWebVC: UIViewController {
    
    var webView: WKWebView!
    var package: NSDictionary!
    var progressView: UIProgressView!
    
    //init
    override func loadView() {
        //add webview
        webView = WKWebView()
        webView.navigationDelegate = self
        view = webView
        
        //add progresbar to navigation bar
        progressView = UIProgressView(progressViewStyle: .default)
        progressView.autoresizingMask = [.flexibleWidth, .flexibleTopMargin]
        progressView.tintColor = #colorLiteral(red: 0.6576176882, green: 0.7789518833, blue: 0.2271372974, alpha: 1)
        navigationController?.navigationBar.addSubview(progressView)
        let navigationBarBounds = self.navigationController?.navigationBar.bounds
        progressView.frame = CGRect(x: 0, y: navigationBarBounds!.size.height - 2, width: navigationBarBounds!.size.width, height: 2)
    }
    
    //deinit
    deinit {
        //remove all observers
        webView.removeObserver(self, forKeyPath: "title")
        webView.removeObserver(self, forKeyPath: "estimatedProgress")
        //remove progress bar from navigation bar
        progressView.removeFromSuperview()
    }

    //viewcontroller
    override func viewDidLoad() {

        webView.load(myRequest())
        webView.allowsBackForwardNavigationGestures = true
        // // add observer for key path
        webView.addObserver(self, forKeyPath: "title", options: .new, context: &myContext)
        webView.addObserver(self, forKeyPath: "estimatedProgress", options: .new, context: &myContext)
    }

    
    
    //actions
    func doneTapped() {
      //Routing is your class handle view routing in your app
        Routing.showAnotherVC(fromVC: self)
    }
    
    //observer
    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        
        guard let change = change else { return }
        if context != &myContext {
            super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
            return
        }
        
        if keyPath == "title" {
            if let title = change[NSKeyValueChangeKey.newKey] as? String {
                self.navigationItem.title = title
            }
            return
        }
        if keyPath == "estimatedProgress" {
            if let progress = (change[NSKeyValueChangeKey.newKey] as AnyObject).floatValue {
                progressView.progress = progress;
            }
            return
        }
    }

    //compute your url request
    func myRequest() -> URLRequest {
        return URLRequest(url: (URL(string: "https://google.com")
    }
    
    func addDoneButton() {
        let done = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(doneTapped))
        navigationItem.rightBarButtonItems = [done]
    }

    func hideBackButton() {
        navigationItem.setHidesBackButton(true, animated: false)
    }
}

extension PaymentVC: WKNavigationDelegate {
    
    //WKNavigationDelegate
    func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
        
        if let url = navigationAction.request.url {
            if url.absoluteString.contains("/something") {
                // if url contains something; take user to native view controller
                Routing.showAnotherVC(fromVC: self)
                decisionHandler(.cancel)
            } else if url.absoluteString.contains("done") {
              //in case you want to stop user going back
                hideBackButton()
                addDoneButton()
                decisionHandler(.allow)
            } else if url.absoluteString.contains("AuthError") {
                //in case of erros, show native allerts
            }
            else{
                decisionHandler(.allow)
            }
        }
    }
   
    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        progressView.isHidden = true
    }
    
    func webView(_ webView: WKWebView, didStartProvisionalNavigation navigation: WKNavigation!) {
        progressView.isHidden = false
    }
}

Looks great, I used parts of it. But I think you have to add the observers before webview.load()?

Can you please help solving "Block Based KVO Violation: Prefer the new block based KVO API with keypaths when using Swift 3.2 or later. (block_based_kvo)" warning while using wkwebview progress bar

Great! The use of observer solved my problem i.e. webview content is loaded first followed by title for navigation item.

However, use of this function throws a warning Block based KVO violation.. Refer screenshot for detail.

Any fix for this?

       var observers: [NSKeyValueObservation] = []
       let obs = webView.observe(\.title, options: .new) {[weak self] webView, _ in
            self?.navBarTitle?.text = webView.title
        }
        observers.append(obs)
        let progressObs = webView.observe(\.estimatedProgress, options: .new) {[weak self] webView, _ in
            self?.progressView.progress = Float(webView.estimatedProgress)
        }
        observers.append(progressObs)
        let isLoadingObs = webView.observe(\.isLoading, options: .new) {[weak self] webView, _ in
            self?.progressView.isHidden = webView.isLoading
        }
        observers.append(isLoadingObs)