WKWebView and NSURLProtocol not working
When using the old UIWebView you could catch the requests by implementing a custom NSURLProtocol. I us this to handle requests that requires authentication.
I tried the same code and it doesn't work with the new WKWebView but my protocol class isn't called at all. Is someone experiencing the same problem or is there a better way of doing authentication with the WKWebView?
Without any modifications I get a 401 response in the decidePolicyForNavigationResponse delegate function. I've also tried connection to the server with a NSURLConnection and handling the authentication with a NSURLConnectionDataDelegate. That works but the stored credentials isn't picked up by the WKWebView.
Answer
Updated answer for iOS 11 and macOS 10.13
Since iOS 11 it is possible to declare an object that conforms to the WKURLSchemeHandler protocol and register it in the WKWebView configuration: -[WKWebViewConfiguration setURLSchemeHandler:forURLScheme:].
Old answer
WKWebView makes requests and renders content out-of-process, meaning your app does not hear the requests they make. If you are missing a functionality, now is the time to open a bug report and/or an enhancement request with Apple.
As of iOS 10.3 SDK, WKWebView is still unable to make use of custom NSURLProtocols using public APIs.
Enterprising developers have found an interesting method:
+[WKBrowsingContextController registerSchemeForCustomProtocol:]
It supposedly adds the provided scheme to a list of custom protocol handled schemes and should then work with NSURLProtocol.