// 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.)
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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!") } } }