Unable to store selected Picker value in SwiftUI-CodePudding

I have a simple SwiftUI view with a Picker containing a list of objects from a data array. The Picker lists the objects just fine, but the selected value is not being saved to the binding variable $selectedCar. It returns empty string. This is the view in question:

struct GarageSpace: View {

var currentUserID: String
@Environment(\.presentationMode) var presentationMode

@Binding var selectedPlaceID: String
@Binding var selectedPlaceName: String
@Binding var selectedPlaceDate: Date
@Binding var selectedSpaceID: String
@State var selectedCar: String
@Binding var cars: CarArrayObject

var body: some View { 
    VStack{
        Group{
            
            Picker("Car", selection: $selectedCar) {
            if let cars = cars{
                ForEach(cars.dataArray, id: \.self) {car in
                    let year = car.year! as String
                    let make = car.make as String
                    let model = car.model! as String
                    let string = year   " "   make   " "   model
                    
                    Text(string) //displays correctly in Picker
                }
            }
        }
            Spacer()
            if let cars = cars {
                Button {
                    print("yes")
                    print(selectedCar) //returns empty string
                } label: {
                    Text("Confirm")
                }
            }
        }
    }
}
}

The above view is displayed via a NavigationLink on the previous screen:

NavigationLink(destination: GarageSpace(currentUserID: currentUserID, selectedPlaceID: $selectedPlaceID, selectedPlaceName: $selectedPlaceName, selectedPlaceDate: $selectedPlaceDate, selectedSpaceID: $selectedSpaceID, selectedCar: "", cars: $cars)) {
                    
                }

This NavigationLink might be the culprit because I'm sending an empty string for selectedCar. However, it forces me to initialize a value with the NavigationLink.

Any ideas? Thanks!

EDIT: Added a tag of type String, still same outcome:

Text(string).tag(car.carID)

EDIT: FOUND THE ISSUE! However, I'm still stumped. The selection variable is empty because I wasn't pressing on the Picker since I only had one item in the array. How can I get the Picker to "select" an item if it's the only one in the array by default?

CodePudding user response：

With tag, all works well in my simple tests. Here is my test code:

import SwiftUI

@main
struct TestApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}
struct ContentView: View {
    var body: some View {
        GarageSpace()
    }
}
struct GarageSpace: View {
    @State var selectedCar: String = ""
    @State var cars: CarArrayObject? = CarArrayObject(car: CarModel(make: "Ford"))
    
    var body: some View {
        VStack {
            Group {
                Picker("Car", selection: $selectedCar) {
                    if let cars = cars {
                        ForEach(cars.dataArray, id: \.self) { car in
                            Text(car.make).tag(car.carID)
                        }
                    }
                }
                Spacer()
                if let cars = cars {
                    Button {
                        print("----> selectedCar carID: \(selectedCar)")
                    } label: {
                        Text("Show selected carID")
                    }
                }
            }
        }
        // optional, to select the first car
        .onAppear {
            if let cars = cars {
                selectedCar = (cars.dataArray.first != nil) ? cars.dataArray.first!.carID : ""
            }
        }
    }
    
}
struct CarModel: Hashable {
    var make = ""
    var carID = UUID().uuidString
}

class CarArrayObject: ObservableObject{
    // for testing
    @Published var dataArray = [CarModel(make: "Toyota"), CarModel(make: "Suzuki"), CarModel(make: "VW")]
    
    /// USED FOR SINGLE CAR SELECTION
    init(car: CarModel) {
        self.dataArray.append(car)
    }
    
    /// USED FOR GETTING CARS FOR USER PROFILE
    init(userID: String) {
//        print("GET CARS FOR USER ID \(userID)")
//        DataService.instance.downloadCarForUser(userID: userID) { (returnedCars) in
//
//            let sortedCars = returnedCars.sorted { (car1, car2) -> Bool in
//                return car1.dateCreated > car2.dateCreated
//            }
//            self.dataArray.append(contentsOf: sortedCars)
//        }
    }
}