Sending message to WKWebView throws error

Question

I am using WKWebView to load HTML in the popup of my Safari App Extension. I am trying to send a message to this page using webView.evaluateJavaScript("myFunction()") but it fails with error message EXC_BREAKPOINT (code=EXC_I386_BPT, subcode=0x0).

I thought the page isn't loaded in the webView at first and hence throws this error but that is not the case here. The page loads completely but I get this error for some reason. Here is my code.

@IBOutlet var webView: WKWebView!

func webView(_ webView: WKWebView,didFinish navigation: WKNavigation!) {
     webView.evaluateJavaScript("myFunction()", completionHandler: nil)   
}

override func viewDidLoad() {
    super.viewDidLoad()
    webView.configuration.userContentController.add(self, name: "popup")
    webView.configuration.userContentController.add(self, name: "print")
    webView.navigationDelegate = self
    view.addSubview(webView!)
    self.view = webView

    if let url = Bundle.main.url(forResource: "MyPopup", withExtension: "html") {
        webView.loadFileURL(url, allowingReadAccessTo: url.deletingLastPathComponent())
    }     
}

I tried checking error inside the completionHandler but it doesn't go there. Any Ideas?

Answer 1

I believe you need to use main thread to execute JS in the webView. Try wrapping the call to webView.evaluateJavaScript() in DispatchQueue.main.async { }.