WebKit Observers

Observers.swift

// WebView Observers
var webViewURLObserver: NSKeyValueObservation?          // Observer for URL
var webViewTitleObserver: NSKeyValueObservation?        // Observer for Page Title
var webViewProgressObserver: NSKeyValueObservation?     // Observer for Load Progress

override func viewDidLoad() {
    super.viewDidLoad()
    
    // OBSERVER: WebView URL
    webViewURLObserver = webView.observe(\.url, options: .new) { [weak self] webView, change in
        let url = "\(String(describing: change.newValue))"
        self?.urlDidChange(urlString: url)
    }
    
    // OBSERVER: WebView Page Title
    webViewTitleObserver = webView.observe(\.title, options: .new) { [weak self] webView, change in
        if let title = change.newValue as? String {
            self?.titleDidChange(pageTitle: title)
        }
    }
    
    // OBSERVER: WebView Load Progress
    webViewProgressObserver = webView.observe(\.estimatedProgress, options: .new) { [weak self] webView, change in
        self?.progressDidChange(progress: change.newValue ?? 1.0)
    }
}

func urlDidChange(urlString: String) {
    if let url = urlString as? String {
        print("URL: \(url)")
    }
}

func titleDidChange(pageTitle: String) {
    let title = pageTitle
    print("Page Title: \(title)")
}

func progressDidChange(progress: Double) {
    let value = Float(progress)     // (range: 0...1; 1 = 100%)
}

ProgressObserver.swift

// WebKit: Page Load Progress Observer Example
var webViewProgressObserver: NSKeyValueObservation?

@IBOutlet var progressBar: UIProgressView!          // iOS Progress Bar
@IBOutlet var progressBar: NSProgressIndicator!     // macOS Progress Spinner

override func viewDidLoad() {
    super.viewDidLoad()
    
    webViewProgressObserver = webView.observe(\.estimatedProgress, options: .new) { [weak self] webView, change in
        self?.progressDidChange(progress: change.newValue ?? 1.0)
    }
}

func progressDidChange(progress: Double) {
    let value = Float(progress)             // Set value as Float for Progress Indicator
    if value < 1 {                          // While page is loading:
        progressBar.isHidden = false        // Show progress bar
        progressBar.progress = value        // Set value of progress indicator
    } else {                                // When page is done loading:
        progressBar.isHidden = true         // Hide progress bar
    }
    print("Loading: \(value)")              // Print page load progress to console
}

TitleObserver.swift

// WebKit: Title Observer Example
var webViewTitleObserver: NSKeyValueObservation?

override func viewDidLoad() {
    super.viewDidLoad()
    
    webViewTitleObserver = webView.observe(\.title, options: .new) { [weak self] webView, change in
        let title = "\(String(describing: change.newValue))"
        self?.titleDidChange(pageTitle: title)
    }
}

func titleDidChange(pageTitle: String) {
    if let title = pageTitle as? String {
        if !title.contains("about:blank") {
            // Detect _blank targets and new windows
        } else {
            self.title = title
        }
    }
}

URLObserver.swift

// WebKit: URL Observer Example
var webViewURLObserver: NSKeyValueObservation?

override func viewDidLoad() {
    super.viewDidLoad()
    
    webViewURLObserver = webView.observe(\.url, options: .new) { [weak self] webView, change in
        let url = "\(String(describing: change.newValue))"
        self?.urlDidChange(urlString: url)
    }
}

func urlDidChange(urlString: String) {
    if let url = urlString as? String {
        if url.contains("404") {
            print("Error 404: Page not found")
        }
    }
}