Load custom error htmlString when WKWebView loadRequest fails

Question

In my controller I have a call to WKWebViewInstance.loadRequest(url). If there is no internet available, I want to load an error message in the WKWebView.

I have found that

  func webView(webView: WKWebView, didFailProvisionalNavigation navigation: WKNavigation!, withError error: NSError) 

gets called when a WKWEbView navigation fails with no internet connection. When I make the webView.loadHtmlString() call inside the above delegate method, nothing happens.

How do I detect the absence of network connection while WKWEbView navigation request is made and load a fixed error message into web view instead?

My delegate method code is

   func webView(webView: WKWebView, didFailProvisionalNavigation navigation: WKNavigation!, withError error: NSError) {
    webView.stopLoading()
    webView.loadHTMLString(Constants.OfflineHtmlString!,baseURL:  nil)
}

Answer 1

IF the need is to display error Info to the user when not connected to internet,

You can check if you are connected to the internet even before loading the request; Reachability is a popular api that usually helps checking this. There seems to be a swift port of it here https://github.com/ashleymills/Reachability.swift

I recommend to pursue the above option; In case you still want to allow it to fail and then display the error, Ensure the correctness of your OfflineHtmlString and verify the error code before loading the OfflineHtmlString;

I don't know if your html string is valid; Provided it is valid, i would do something like below;

func webView(webView: WKWebView, didFailProvisionalNavigation navigation: WKNavigation!, withError error: NSError) {
   if(error.code == NSURLErrorNotConnectedToInternet){
       webView.loadHTMLString(Constants.OfflineHtmlString!,baseURL:  nil)
   }
}

Answer 2

Subbu is correct just for swift4

    func webView(_ webView: WKWebView, didFailProvisionalNavigation navigation: WKNavigation!, withError error: Error) {
    print("loading error", error)
    if(error._code == NSURLErrorNotConnectedToInternet){
        loadingLabel.text = "Hit Cancel to return back"
    }
    errorDisplay(error: "Loading error. Please try again later.\(error)")
    spinner.stopAnimating()
    loadingLabel.text = "Hit Cancel to return back"
}

Answer 3

Seems that loadingHTMLString won't work if you don't set the baseURL. If you don't have a valid URL you can use a Data URL.

This is what worked for me:

func webView(_ webView: WKWebView, didFailProvisionalNavigation navigation: WKNavigation!, withError error: Error) {
    if let urlError = error as? URLError {
        webView.loadHTMLString(urlError.localizedDescription, baseURL: urlError.failingURL)
    } else {
        webView.loadHTMLString(error.localizedDescription, baseURL: URL(string: "data:text/html"))
    }
}