Swift version: 5.0
WKUIDelegate protocol is for you.
First, make your view controller conform to it by adding
WKUIDelegate to its list of protocols. Second, assign your view controller to the
uiDelegate property of your web view:
yourWebView.uiDelegate = self
Finally, implement whichever of the optional methods of
WKUIDelegate takes your interest. For example, you can make
WKWebView show a custom alert controller when any web page uses the
Available from iOS 10.0
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