Using SwiftUI ForEach's iterator variable in a binding call

Question

I am trying to use ForEach's iterator variable in a view that requires binding.

import SwiftUI

struct MyStruct: Identifiable {
    public var id = UUID()
    var name: String
    var repetitions: Int

}

struct ContentView: View {
    @State private var mystructs :[MyStruct] = [
        MyStruct(name: "John", repetitions: 3),
        MyStruct(name: "Mark", repetitions: 9)
    ]

    var body: some View {

        List {
            ForEach (mystructs) { st in
                VStack {
                    Text("\(st.name)")
                    TextField("Name", text: self.$mystructs[0].name)
                    TextField("Name", text: $st.name) // <- Got "Ambiguous reference..." error
                }
            }
        }
    }
}

The ForEach iterator works, as demonstrated by the Text view's use of st.name. And the first TextField demonstrates that binding to mystructs' element works. However, for the second TextField which is my real use case, causes the following compiler errors:

- Use of unresolved identifier $st
- Ambiguous reference to member of 'subscript'

Any thoughts?

Trying to make the list dynamic where I can add/delete elements of array and at the same time modify the elements. This is a simplified code snippet; in my code I have a custom View instead of TextField and requires a binding. — Hampden123
– Hampden123, Commented Feb 13, 2020 at 16:20

Anjali Aggarwal · Accepted Answer · 2020-02-13 14:59:18Z

1

$st is coming as unresolved as 'st' is not a state variable and cannot be used for binding purpose.
Also $mystructs is working because it is a declared as a State variable and can be used for binding.

Hope this is of some use for you!Thanks!

answered Feb 13, 2020 at 14:59

Anjali Aggarwal

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Asperi · Accepted Answer · 2020-02-13 16:24:23Z

1

In the described scenario it can be done the following

ForEach (mystructs.indices) { i in
    VStack {
        Text("\(self.mystructs[i].name)")
        TextField("Name", text: self.$mystructs[i].name)
    }
}

Update: variant for more generic use-case

ForEach (Array(mystructs.enumerated()), id: \.element.id) { (i, item) in
    VStack {
        Text("\(item.name)")
        TextField("Name", text: self.$mystructs[i].name)
    }
}

edited Feb 13, 2020 at 16:24

answered Feb 13, 2020 at 15:00

Asperi

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2 Comments

Hampden123 Over a year ago

Thanks but unfortunately in my real use case the number of elements in the array would also change. E.g. if somewhere in the view a button appends another element to the array, the view would NOT display the new element because the count would stay constant, despite no compiler error.

Asperi Over a year ago

@Hampden123, there is variant for generic case as well, please see update.

markiv · Accepted Answer · 2020-02-13 16:54:24Z

1

Building on @Asperi's answer, this also works:

var body: some View {
    List {
        Button("Add") {
            self.mystructs.append(MyStruct(name: "Pepe", repetitions: 42))
        }
        ForEach(mystructs.indices, id: \.self) { index in
            VStack {
                Text(self.mystructs[index].name)
                TextField("Name", text: self.$mystructs[index].name)
            }
        }
    }
}

answered Feb 13, 2020 at 16:54

markiv

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