It seems that the IB object templates in XCode 6 beta are still creating old-style objects (UIWebView for iOS and WebView for OSX). Hopefully Apple will update them for the
You can instantiate and configure a WKWebView in IB since Xcode 9, no need to do it in code.
Note that your deployment target has to be higher than iOS 10 though or you will get a compile-time error.