UIWebView.loading returns false - ios

Question

With swift using the following code:
super.viewDidLoad()
let webView = UIWebView(frame: self.view.bounds)
view.addSubview(webView)
let URL = NSURL(string: "http://www.google.com")
webView.loadRequest(NSURLRequest(URL: URL!))
println(webView.loading)
It prints false and the screen is blank. How is this resolved?

Answer 1

This is perfectly normal behaviour. The UIWebView does not actually start loading content until the UI event, in this case viewDidLoad, has finished executing. So checking it immediately returns false because it has not started just yet.
If you want want to track the success or failure of the UIWebView you should implement the UIWebViewDelegate in your view controller. That way you get callbacks when the request has finished loading or if it has failed.

Answer 2

I'm uncertain exactly on the internals of how UIWebView loads its data or what exactly happens when you call loadRequest, but contrary to my expectations, nothing seems to actually happen until the method which called loadRequest has returned.
Consider the following code:
#IBAction func buttonPress(sender: UIButton) {
let webview = UIWebView(frame: self.view.bounds)
view.addSubview(webview)
let url = NSURL(string: "http://www.google.com")
webview.delegate = self
webview.loadRequest(NSURLRequest(URL: url!))
println("buttonPress: webview.loading? \(webview.loading)")
}
func webView(webView: UIWebView, shouldStartLoadWithRequest request: NSURLRequest, navigationType: UIWebViewNavigationType) -> Bool {
println("webview asking for permission to start loading")
return true
}
func webViewDidStartLoad(webView: UIWebView) {
println("webview did start loading")
}
func webView(webView: UIWebView, didFailLoadWithError error: NSError) {
println("webview did fail load with error: \(error)")
}
func webViewDidFinishLoad(webView: UIWebView) {
println("webview did finish load!")
}
Here, the println in the buttonPress method always executes before any of the other methods. In fact, seemingly no matter what sort of code we put after the loadRequest call, it all executes before the web view even asks shouldStartLoadingWithRequest:.
webview.loadRequest(NSURLRequest(URL: url!))
for _ in 1...10000 {
println("buttonPress: webview.loading? \(webview.loading)")
}
Ten thousand iterations, and yet nothing starts for the webview until after buttonPress method returns.
Meanwhile, webview.loading will only return true between webViewDidStartLoad and one of the two ways the load can stop (failure/success) (webView(webView:didFailLoadWithError:) or webViewDidFinishLoad()).
IF you implement the UIWebViewDelegate protocol and set the web view's delegate, you can implement these methods to keep track of the loading process. If, for whatever reason, your web view isn't loading the URL, implementing webView(webView:didFailLoadWithError:) is the only way to get any sort of diagnostic informatin to determine what failed with the load.