WKWebView causes my view controller to leak

Question

My view controller displays a WKWebView. I installed a message handler, a cool Web Kit feature that allows my code to be notified from inside the web page:

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Answer 1

Details

• Swift 5.1
• Xcode 11.6 (11E708)

Solution

based on Matt's answer

protocol ScriptMessageHandlerDelegate: class {
    func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage)
}

class ScriptMessageHandler: NSObject, WKScriptMessageHandler {

    deinit { print("____ DEINITED: \(self)") }
    private var configuration: WKWebViewConfiguration!
    private weak var delegate: ScriptMessageHandlerDelegate?
    private var scriptNamesSet = Set()

    init(configuration: WKWebViewConfiguration, delegate: ScriptMessageHandlerDelegate) {
        self.configuration = configuration
        self.delegate = delegate
        super.init()
    }

    func deinitHandler() {
        scriptNamesSet.forEach { configuration.userContentController.removeScriptMessageHandler(forName: $0) }
        configuration = nil
    }
    
    func registerScriptHandling(scriptNames: [String]) {
        for scriptName in scriptNames {
            if scriptNamesSet.contains(scriptName) { continue }
            configuration.userContentController.add(self, name: scriptName)
            scriptNamesSet.insert(scriptName)
        }
    }

    func userContentController(_ userContentController: WKUserContentController,
                               didReceive message: WKScriptMessage) {
        delegate?.userContentController(userContentController, didReceive: message)
    }
}

Full Sample

Do not forget to paste the Solution code here

import UIKit
import WebKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        let button = UIButton(frame: CGRect(x: 0, y: 0, width: 100, height: 40))
        button.setTitle("WebView", for: .normal)
        view.addSubview(button)
        button.center = view.center
        button.addTarget(self, action: #selector(touchedUpInsed(button:)), for: .touchUpInside)
        button.setTitleColor(.blue, for: .normal)
    }
    
    @objc func touchedUpInsed(button: UIButton) {
        let viewController = WebViewController()
        present(viewController, animated: true, completion: nil)
    }
}

class WebViewController: UIViewController {

    private weak var webView: WKWebView!
    private var scriptMessageHandler: ScriptMessageHandler!
    private let url = URL(string: "http://google.com")!
    deinit {
        scriptMessageHandler.deinitHandler()
        print("____ DEINITED: \(self)")
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        let configuration = WKWebViewConfiguration()
        scriptMessageHandler = ScriptMessageHandler(configuration: configuration, delegate: self)
        let scriptName = "GetUrlAtDocumentStart"
        scriptMessageHandler.registerScriptHandling(scriptNames: [scriptName])

        let jsScript = "webkit.messageHandlers.\(scriptName).postMessage(document.URL)"
        let script = WKUserScript(source: jsScript, injectionTime: .atDocumentStart, forMainFrameOnly: true)
        configuration.userContentController.addUserScript(script)
        
        let webView = WKWebView(frame: .zero, configuration: configuration)
        self.view.addSubview(webView)
        self.webView = webView
        webView.translatesAutoresizingMaskIntoConstraints = false
        webView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        webView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
        view.bottomAnchor.constraint(equalTo: webView.bottomAnchor).isActive = true
        view.rightAnchor.constraint(equalTo: webView.rightAnchor).isActive = true
        webView.load(URLRequest(url: url))
    }
}

extension WebViewController: ScriptMessageHandlerDelegate {
    func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
        print("received \"\(message.body)\" from \"\(message.name)\" script")
    }
}

Info.plist

add in your Info.plist transport security setting

NSAppTransportSecurity

    NSAllowsArbitraryLoads