Can a class instance in a View struct interact with the view's State variable?

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td540 OP

Created Apr ’21

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SwiftUI question: (How) Can the myClass instance in this View interact with a State variable?

Not working:

Code Block struct MyView: View {       @State private var hello = "world"       let myClass = MyClass()       class MyClass: NSObject, WKScriptMessageHandler {              func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {                   if message.name == "hello"{                        hello = message.body                   }       }       // ...}

by the way, I’m adding myClass to a webview’s configuration.userContentController. The userContentController in the class gets called when javascript calls window.webkit.messageHandlers.hello.postMessage("new world")

Thank you kindly

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Answer 1

td540 OP

Apr ’21

Here's code for my completed use case:

Code Block  swiftimport SwiftUIimport WebKitimport WebView /* Using Swift Package Dependency: https://github.com/kylehickinson/SwiftUI-WebView */struct ContentView: View {    @StateObject private var webViewStore: WebViewStore    @State private var hello = "SwiftUI world"    class MyClass: NSObject, WKScriptMessageHandler {        func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {            if message.name == "hello" {                print(message.body) /* this works */                /* but how do I change ContentView's hello State from here? */            }       }    }    init() {        let userContentController = WKUserContentController()        let configuration = WKWebViewConfiguration()        let userScript = WKUserScript(            source: """              function elementReady(selector) {                return new Promise((resolve, reject) => {                  let el = document.querySelector(selector)                  if (el) {                    resolve(el)                  }                  new MutationObserver((mutationRecords, observer) => {                    Array.from(document.querySelectorAll(selector)).forEach((element) => {                      resolve(element)                      observer.disconnect()                    })                  }).observe(document.documentElement, {                    childList: true,                    subtree: true,                  })                })              }              elementReady("h1").then((titleElement) => {                window.webkit.messageHandlers.hello.postMessage(titleElement.textContent)              })            """,            injectionTime: .atDocumentStart,            forMainFrameOnly: false,            in: .defaultClient        )        let myClass = MyClass()        userContentController.add(myClass, contentWorld: .defaultClient, name: "hello")        userContentController.addUserScript(userScript)        configuration.userContentController = userContentController        let webView = WKWebView(frame: .zero, configuration: configuration)        _webViewStore = StateObject(wrappedValue: WebViewStore(webView: webView))    }    var body: some View {        Text("Hello \(hello)")        WebView(webView: webViewStore.webView)            .onAppear {                webViewStore.webView.loadHTMLString("<h1>JS world</h1>", baseURL: nil)                /* I'll be loading any kind of webpage here */            }        Button("load new world") {            /* load new page with h1 tag */            webViewStore.webView.loadHTMLString("<h1>new world</h1>", baseURL: nil)        }    }}struct ContentView_Previews: PreviewProvider {    static var previews: some View {        ContentView()    }}

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