Why does picker binding not update when using SwiftUI? - swift

Question

I have just begun learning Swift (and even newer at Swift UI!) so apologies if this is a newbie error.
I am trying to write a very simple programme where a user chooses someone's name from a picker and then sees text below that displays a greeting for that person.
But, the bound var chosenPerson does not update when a new value is picked using the picker. This means that instead of showing a greeting like "Hello Harry", "Hello no-one" is shown even when I've picked a person.
struct ContentView: View {
var people = ["Harry", "Hermione", "Ron"]
#State var chosenPerson: String? = nil
var body: some View {
NavigationView {
Form {
Section {
Picker("Choose your favourite", selection: $chosenPerson) {
ForEach ((0..<people.count), id: \.self) { person in
Text(self.people[person])
}
}
}
Section{
Text("Hello \(chosenPerson ?? "no-one")")
}
}
}
}
}
(I have included one or two pieces of the original formatting in case this is making a difference)
I've had a look at this question, it seemed like it might be a similar problem but adding .tag(person) to Text(self.people[person])did not solve my issue.
How can I get the greeting to show the picked person's name?

Answer 1

Bind to the index, not to the string. Using the picker, you are not doing anything that would ever change the string! What changes when a picker changes is the selected index.
struct ContentView: View {
var people = ["Harry", "Hermione", "Ron"]
#State var chosenPerson = 0
var body: some View {
NavigationView {
Form {
Section {
Picker("Choose your favourite", selection: $chosenPerson) {
ForEach(0..<people.count) { person in
Text(self.people[person])
}
}
}
Section {
Text("Hello \(people[chosenPerson])")
}
}
}
}
}

Answer 2

The accepted answer is right if you are using simple arrays, but It was not working for me because I was using an array of custom model structs with and id defined as string, and in this situation the selection must be of the same type as this id.
Example:
struct CustomModel: Codable, Identifiable, Hashable{
var id: String // <- ID of type string
var name: String
var imageUrl: String
And then, when you are going to use the picker:
struct UsingView: View {
#State private var chosenCustomModel: String = "" //<- String as ID
#State private var models: [CustomModel] = []
var body: some View {
VStack{
Picker("Picker", selection: $chosenCustomModel){
ForEach(models){ model in
Text(model.name)
.foregroundColor(.blue)
}
}
}
Hope it helps somebody.