Script message handler not working

Question

I am trying to inject a custom WebKit script message handler. My controller is correctly loaded and the view as well. However, on the JS side (from the Safari console), window.webkit.messageHandlers is empty. Any idea why? My app is using iOS 8.1 but even by upgrading to 9.2, it did not work.

import Foundation
import UIKit
import WebKit

public class FooController: UIViewController, WKScriptMessageHandler {
    private var wkWebView: WKWebView?

    public override func viewDidLoad() {
        super.viewDidLoad()

        let o = WKUserContentController()
        o.addScriptMessageHandler(self, name: "foo")
        let config = WKWebViewConfiguration()
        config.userContentController = o

        self.wkWebView = WKWebView(frame: self.view.bounds, configuration: config)
        self.view.addSubview(self.wkWebView!)

        self.wkWebView!.loadRequest(NSURLRequest(URL: NSBundle.mainBundle().URLForResource("foo", withExtension: "html")!))
    }

    public func userContentController(userContentController: WKUserContentController, didReceiveScriptMessage message: WKScriptMessage) {
        print("foo")
    }
}

Solution

webkit.messageHandlers is not an Array. It is a UserMessageHandlersNamespace.

Try

var message = {"key1":"value1", "key2":"value2", "dictionary": {"name": "foo"}}
webkit.messageHandlers.foo.postMessage(message);

In your message handler.

public func userContentController(userContentController: WKUserContentController, didReceiveScriptMessage message: WKScriptMessage) {
    let body = message.body
    if let dict = body as? Dictionary<String, AnyObject> {
        print(dict)
    }
}

Comments

[Adrien Cadet]

Hey Onato, thanks for your answer. I know messageHandlers is an object. But it has no key at all, and especially foo is missing.

[Onato]

Your swift code worked fine for me. Can you post how you are calling your message handler or checking for the existence of "foo"?

[Adrien Cadet]

Arf. Just retested and it works fine. Sorry for the confusion. However, I have a different issue now. I cannot post any custom data. I tried to post a dictionary with 2 strings and another dictionary and the body I received only included a single string. Not a big deal, but do you know anything about that?

[Adrien Cadet]

Awesome! It works fine. I was trying to cast the body as a NSDictionary but it did not work as expected.