How to connect asyc data fetch using Core NFC and Swift UI?

Question

I am trying to create a DataModel for my SwiftUI Screen. The problem I am facing is that I use Core NFC to scan a NFCTag (perform some tasks) and then I want to update the SwiftUI Screen. The data fetch/manipulation occurs asynchronous.

View

struct NFCTest: View {

    @EnvironmentObject var nfcController: NFCController


    var body: some View {
        VStack {
            Button(action: {
                self.nfcController.beginScanning()
            }) {
                Text("Button")
            }

NFCController

final class NFCController: UIViewController, ObservableObject {

@Published var someObject :ObjectStruct //someObject contains a @Published var someVar    
//Tag detected
    func doSomeAsyncCalls {
    //calling functions in other swift files. runs async on another thread. Should change someVar at the end of the calculation
    }

Now the problem is that nested Observable Objects to do not work in SwiftUI. I tried to make an observable var in NFCController and inside that var I created a published var. But the change is not triggered in SwiftUI.

Are there any concepts to solve this async data flow problem?

Answer 1

Here is possible approach (scratchy)

final class NFCController: UIViewController, ObservableObject {

    @Published var someObject :ObjectStruct

    func doSomeAsyncCalls {

        // .. some other code here
        DispatchQueue.global(qos: .background).async { // < mimic async call
            // .. some calculations

            DispatchQueue.main.async {
                self.someObject.someVar = result
                self.objectWillChange.send()     // << here !!
            }
        }
    }
}

of course related view should has dependency on this controller members somewhere in body, otherwise rendering engine could just ignore update.