AlamoFire UI lockup fix

fix.swift

import SwiftUI
import Alamofire
import Combine

struct ContentView: View {
    @StateObject var viewModel: ViewModel = ViewModel()
    @State private var showAlert = false
    @State private var downloadProgress: Double = 0.0

    var body: some View {
        VStack {
            Button("Show Alert") {
                showAlert.toggle()
            }
            
            Button("Start download") {
                viewModel.startDownload()
            }
            
            if viewModel.showProgressView {
                ProgressView("Downloading…", value: viewModel.downloadProgress, total: 1.0)
                    .progressViewStyle(.linear)
            }
        }
        .alert(isPresented: $showAlert) {
            Alert(
                title: Text("Text"),
                message: Text("Dismiss this"),
                dismissButton: .cancel()
            )
        }
    }
}

class ViewModel: ObservableObject {
    @Published var showProgressView: Bool = false
    @Published var downloadProgress = 0.0
    
    func startDownload() {
        let queue = DispatchQueue(label: "net", qos: .userInitiated)
        
        showProgressView.toggle()
        
        let destination = DownloadRequest.suggestedDownloadDestination(for: .documentDirectory)
        var last = Date()
        
        AF.download("https://speed.hetzner.de/100MB.bin", to: destination)
            .downloadProgress { progress in
                print(progress.fractionCompleted)
                if Date().timeIntervalSince(last) > 1 {
                    last = Date()
                    DispatchQueue.main.async {
                        self.downloadProgress = progress.fractionCompleted
                    }
                }
            }
            .response(queue: queue) { response in
                print(response)
            }
        
    }
}