Hi everyone,

I am working on an app and would like to add a picker, but I get the message "Picker: the selection "nil" is invalid and does not have an associated tag, this will give undefined results" in the log. What can I do? Thx

Destination.swift

import Foundation
import SwiftData

@Model
class Destination {
    var name: String
    var details: String
    var date: Date
    var priority: Int

    @Relationship(deleteRule: .cascade) var personen = [Personen]()
    @Relationship(deleteRule: .cascade) var kosten = [Kosten]()

    init(name: String = "", details: String = "", date: Date = .now, priority: Int = 2) {
        self.name = name
        self.details = details
        self.date = date
        self.priority = priority
    }
}

Personen.swift

import SwiftUI
import SwiftData

@Model
class Personen: Identifiable {
    var id: UUID = UUID()
    var name: String
    var destination: Destination?
    @Relationship(deleteRule: .cascade) var kosten = [Kosten]()

    init(id: UUID, name: String = "", destination: Destination? = nil, kosten: [Kosten] = [Kosten]()) {
        self.id = id
        self.name = name
        self.destination = destination
        self.kosten = kosten
    }
}

Kosten.swift

import SwiftUI
import SwiftData

@Model
class Kosten {
    var name: String
    var beitrag: Double
    var anzahl: String
    var destination: Destination?
    var personen: Personen?

    init(name: String, beitrag: Double, anzahl: String, destination: Destination? = nil, personen: Personen? = nil) {
        self.name = name
        self.beitrag = beitrag
        self.anzahl = anzahl
        self.destination = destination
        self.personen = personen
    }
}

EditDestinationView

import SwiftUI
import SwiftData

struct EditDestinationView: View {
    @Bindable var destination: Destination

    @State private var newPersonName = ""
    @State private var newKostenName = ""
    @State private var newKostenBeitrag: Double = .zero
    @State private var newKostenAnzahl = ""

    // For the Popup View
    @State private var showingPopover = false

    @State private var multiSelection: UUID?

    var body: some View {

        Form {
            TextField("Name", text: $destination.name)
            TextField("Details", text: $destination.details, axis: .vertical)
            DatePicker("Date", selection: $destination.date)
                .datePickerStyle(.graphical)
                .background(.background, in: .rect(cornerRadius: 10))
                .accentColor(.purple)

            Section("Währung") {
                Picker("Währung", selection: $destination.priority) {
                    Image(systemName: "dollarsign").tag(1)
                    Image(systemName: "eurosign").tag(2)
                    Image(systemName: "bitcoinsign").tag(3)
                }
                .pickerStyle(.segmented)
            }
            Section("Personen") {
                HStack {
                    TextField("Füge eine Person hinzu", text: $newPersonName)

                    Button("Hinzufügen", action: addSight)
                        .foregroundStyle(.purple)
                }
                ForEach(destination.personen, id: \.id) { personen in
                    Text(personen.name)
                }
            }
            Section("Kosten Hinzufügen") {
                TextField("Kosten Name", text: $newKostenName)

                HStack {
                    if destination.priority == 1 {
                        Image(systemName: "dollarsign")
                    }
                    else if destination.priority == 2 {
                        Image(systemName: "eurosign")
                    }
                    else {
                        Image(systemName: "bitcoinsign")
                    }

                    TextField("", value: $newKostenBeitrag, formatter: numberFormatter)
                        .keyboardType(.decimalPad)

                    TextField("Anzahl je:", text: $newKostenAnzahl)
                }

                Button("Hinzufügen", action: addKosten)
                    .foregroundStyle(.purple)

                ForEach(destination.kosten, id: \.self) { kosten in
                    VStack (alignment: .leading) {
                        Text(kosten.name)
                            .font(.title3)
                            .fontWeight(.bold)

                        Text("Anzahl: \(kosten.anzahl)")
                        HStack {
                            Text("Beitrag (je): \(kosten.beitrag)")

                            if destination.priority == 1 {
                                Image(systemName: "dollarsign")
                            }
                            else if destination.priority == 2 {
                                Image(systemName: "eurosign")
                            }
                            else {
                                Image(systemName: "bitcoinsign")
                            }
                        }
                        Picker("Personen auswählen", selection: $multiSelection) {

                            Text("").tag("")

                            ForEach(destination.personen, id: \.id) { personen in
                                Text(personen.name).tag(personen.id)
                            }
                        }
                        .pickerStyle(.menu).foregroundStyle(.purple)
                    }
                }
            }
        }
        .navigationTitle("Edit Destination")
        .navigationBarTitleDisplayMode(.inline)
    }

    func addSight() {
        guard newPersonName.isEmpty == false else { return }

        withAnimation {
            let person = Personen(id: UUID(), name: newPersonName)
            destination.personen.append(person)
            newPersonName = ""
        }
    }

    func addKosten() {
        /// Um Kosten hinzuzufügen
        guard newKostenName.isEmpty == false else { return }
        guard newKostenAnzahl.isEmpty == false else { return }

        withAnimation {
            let kosten = Kosten(name: newKostenName, beitrag: newKostenBeitrag, anzahl: newKostenAnzahl)
            destination.kosten.append(kosten)
            newKostenName = ""
            newKostenBeitrag = .zero
            newKostenAnzahl = ""
        }
    }

    /// Number Formatter
    var numberFormatter: NumberFormatter {
        let formatter = NumberFormatter()
        formatter.numberStyle = .decimal
        formatter.maximumFractionDigits = 2

        return formatter
    }
}

#Preview {
    do {
        let config = ModelConfiguration(isStoredInMemoryOnly: true)
        let container = try ModelContainer(for: Destination.self, configurations: config)
        let example = Destination(name: "Tacco Laden", details: "Tacco Laden mit der Truppe.")
        return EditDestinationView(destination: example)
            .modelContainer(container)
    } catch {
        return Text("Failes to create container: \(error.localizedDescription)")
    }
}

Consider adding code to your Destination class describing the Image that should be used in views.

Then you can replace this....

HStack {
        if destination.priority == 1 {
            Image(systemName: "dollarsign")
        }
        else if destination.priority == 2 {
            Image(systemName: "eurosign")
        }
        else {
            Image(systemName: "bitcoinsign")
        }
    //. .... more code here.....

with cleaner code such as

HStack {
    // Just declare what you want to see!
    // You want to see the destination image, yes? Then tell this to SwiftUI.
    destination.image // <-- this returns an Image object but is defined INSIDE your Destination class
    // .... more code here....

Thx I think i fix it but I have another issue.

The Fix

Picker("Kosten auswählen", selection: $kostenAuswahl) {

                            Text("").tag(nil as Kosten?)

                            ForEach(destination.kosten, id: \.self) { kosten in
                                Text(kosten.name).tag(kosten as Kosten?).bold()
                            }
                        }
                        .pickerStyle(.menu).foregroundStyle(.purple)
                    }

Now my problem is in the list of people where the picker is. If I select a "cost" for the person, it is selected for each person. Does anyone have a solution to this?