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How I can return result of js or any function to the screen of iPhone? by ContentView

    //  ContentView.swift
//  Shared

import Foundation
import SwiftUI
import JavaScriptCore

class cube {
    var result: String
    
    func do_js(text: String) -> String {
        
let jsSource = "var testFunct = function(message) { return "Test Message: " + message;}"

var context = JSContext()
context?.evaluateScript(jsSource)

let testFunction = context?.objectForKeyedSubscript("testFunct")
        var result = testFunction?.call(withArguments: [text]).toString()
    return result!
    }
}


struct ContentView: View {
    
    cube().do_js(text: "Hello world") // Starts forom here
    
    var show_text = lol().result
    
    var body: some View {
        Text(show_text)
            .font(.body)
            .fontWeight(.black)
            .foregroundColor(Color.red)
            .padding()
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

(Sorry, I’m beginner and come to swift even not from js, but from python! So it’s incredibly new for me. But js more understandable for me from python.)

enter image description here

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Answer

Here’s the simplest version. In this version, it basically uses your original pattern where doJS returns a value. The disadvantage to this version is that doJS will get called every time the view renders.

class Cube {
    func doJS(text: String) -> String? {
        let jsSource = "var testFunct = function(message) { return "Test Message: " + message;}"

        let context = JSContext()
        context?.evaluateScript(jsSource)

        let testFunction = context?.objectForKeyedSubscript("testFunct")
        return testFunction?.call(withArguments: [text]).toString()
    }
}

struct ContentView: View {
    var body: some View {
        Text(Cube().doJS(text: "Hello, world!") ?? "No result")
            .font(.body)
            .fontWeight(.black)
            .foregroundColor(Color.red)
            .padding()
    }
}

And here’s a slightly different version. In this version, Cube is an ObservableObject with a @Published value that stores the result. It will only get called once in onAppear.

class Cube : ObservableObject {
    @Published var result : String?
    
    func doJS(text: String) {
        let jsSource = "var testFunct = function(message) { return "Test Message: " + message;}"

        let context = JSContext()
        context?.evaluateScript(jsSource)

        let testFunction = context?.objectForKeyedSubscript("testFunct")
        result = testFunction?.call(withArguments: [text]).toString()
    }
}

struct ContentView: View {
    @StateObject var cube = Cube()
    
    var body: some View {
        Text(cube.result ?? "No result")
            .font(.body)
            .fontWeight(.black)
            .foregroundColor(Color.red)
            .padding()
            .onAppear {
                cube.doJS(text: "Hello, world!")
            }
    }
}
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