Load WebView before transitioning to it - ios

Question

I had to update an app that i didn't touch for quite a while and now am facing an 'Fatal error: Unexpectedly found nil while unwrapping an Optional value' in DetailViewController::refreshWebView() when executing webView.loadRequest(myRequest) because webView is nil at this point in time.
I didn't change anything relating to how the DetailViewController is loaded and assigned to MasterViewController, so I am very confused as why this does not work anymore.
Was there something changed that i am not aware of? Or did I implement this whole thing incorrectly in the first place and it was coincidence that it worked?
import UIKit
protocol EventSelectionDelegate: class {
func eventSelected(_ newEvent: String)
}
class MasterViewController: UIViewController, UIWebViewDelegate {
var activityView: UIActivityIndicatorView!
weak var delegate: EventSelectionDelegate?
func detailChosen(_ detailUrlString: String) {
delegate?.eventSelected(detailUrlString)
activityView.startAnimating()
}
func transitionToDetail() {
if let detailViewController = self.delegate as? DetailViewController {
DispatchQueue.main.async {
self.activityView.stopAnimating()
self.splitViewController?.showDetailViewController(detailViewController, sender: nil)
}
}
}
}
// Helper function inserted by Swift 4.2 migrator.
fileprivate func convertToUIApplicationOpenExternalURLOptionsKeyDictionary(_ input: [String: Any]) -> [UIApplication.OpenExternalURLOptionsKey: Any] {
return Dictionary(uniqueKeysWithValues: input.map { key, value in (UIApplication.OpenExternalURLOptionsKey(rawValue: key), value)})
}
import UIKit
class DetailViewController: UIViewController, UIWebViewDelegate {
#IBOutlet weak var webView: UIWebView!
var animationWaitDelegate: MasterViewController!
var eventUrl: String! {
didSet {
self.refreshWebView()
}
}
override func viewDidLoad() {
super.viewDidLoad()
webView.delegate = self
}
func refreshWebView() {
let myURL = URL(string:eventUrl!)
let myRequest = URLRequest(url: myURL!)
webView.loadRequest(myRequest)
}
func webViewDidFinishLoad(_ webView: UIWebView) {
animationWaitDelegate.transitionToDetail()
}
}
extension DetailViewController: EventSelectionDelegate {
func eventSelected(_ newEvent: String) {
eventUrl = newEvent
}
}
// Helper function inserted by Swift 4.2 migrator.
fileprivate func convertToUIApplicationOpenExternalURLOptionsKeyDictionary(_ input: [String: Any]) -> [UIApplication.OpenExternalURLOptionsKey: Any] {
return Dictionary(uniqueKeysWithValues: input.map { key, value in (UIApplication.OpenExternalURLOptionsKey(rawValue: key), value)})
}
PS: I found a workaround in the meantime where I added a flag in DetailViewController that allows me to call refreshWebView in viewDidLoad if webView was nil the first time it was called.

Answer 1

First you have to update following code for null check, which will prevent crashing your app.
func refreshWebView() {
if webView != nil {
let myURL = URL(string:eventUrl!)
let myRequest = URLRequest(url: myURL!)
webView.loadRequest(myRequest)
}
}
After at transition add following code will fix your issue.
func transitionToDetail() {
if let detailViewController = self.delegate as? DetailViewController {
DispatchQueue.main.async {
self.activityView.stopAnimating()
detailViewController.loadViewIfNeeded() // Add this line of code
self.splitViewController?.showDetailViewController(detailViewController, sender: nil)
}
}
}
loadViewIfNeeded() method will load your controls before open screen if required.