WKWebView evaluate JavaScript return value

Question

I need to change a function to evaluate JavaScript from UIWebView to WKWebView. I need to return result of evaluating in this function.

Now, I am calling:

Answer 1

I just stumbled about the same problem and wrote a little Swift (3.0) WKWebView extension for it, thought I might share it:

extension WKWebView {
    func evaluate(script: String, completion: (result: AnyObject?, error: NSError?) -> Void) {
        var finished = false

        evaluateJavaScript(script) { (result, error) in
            if error == nil {
                if result != nil {
                    completion(result: result, error: nil)
                }
            } else {
                completion(result: nil, error: error)
            }
            finished = true
        }

        while !finished {
            RunLoop.current().run(mode: .defaultRunLoopMode, before: Date.distantFuture)
        }
    }
}