Hi all

This is a bit of a head scratcher. I'm running macOS Ventura beta 22A5295h, Xcode beta 3, but I have a feeling my issue with the code below is that I'm fundamentally misunderstanding something.

As background, the wider issue I'm having is one where, after passing a bound string from an observed object to a child view, changes to that string in a SwiftUI TextField have some artifacts: the caret jumps to the end of the string, and keystrokes are lost.

I've come up with a short example below, which doesn't show exactly the same behaviour, but still has the issue that the user cannot successfully edit the bound variable's value. Any ideas what I might be doing wrong? I guess I'm looking for the SwiftUI paradigm that allows editing of bound variable with a list.

//
//  ContentView.swift
//  EditViewTest
//
//  Created by Ian Hocking on 11/07/2022.
//

import SwiftUI

public class ViewModel: ObservableObject, Identifiable {
    @Published var fruitNames: [String] = ["Apple", "Orange"]
}

struct ContentView: View {
    @StateObject var viewModel = ViewModel()

    var body: some View {
        NavigationStack {
            List {
                ForEach($viewModel.fruitNames, id: \.self) { $name in
                    NavigationLink(destination: EditView(text: $name)) {
                        Text(name)
                    }
                }
            }
        }
    }
}

struct EditView: View {
    @Binding var text: String

    var body: some View {
        TextField("Edit this", text: $text)
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

Cheers

Ian

Ian has a question about bindings:

Any ideas what I might be doing wrong?
I guess I'm looking for the SwiftUI paradigm that allows editing of bound variable with a list.

@twoStraws gives a pretty good example in his tutorials.

See -> Pretty good binding example

Not sure I could give a better example. What part of @twoStraw's example doesn't work for you? Try turning your fruit strings into identifiable Fruit objects, with identifiers.

Thanks, @Obelix

What part of @twoStraw's example doesn't work for you?

None. The paradigm I'm looking for is editing bound variables in a list where the data come from a view model, which isn't what the example is designed to demonstrate.

Let's adapt the code to give it a basic view model, which is the first step towards my original example:

import SwiftUI

struct User: Identifiable {
    let id = UUID()
    var name: String
    var isContacted = false
}

class ViewModel: ObservableObject {
    @Published public var users = [
        User(name: "Taylor"),
        User(name: "Justin"),
        User(name: "Adele")
    ]
}

struct ContentView: View {
    @StateObject var viewModel = ViewModel()

    var body: some View {
        List($viewModel.users) { $user in
            Text(user.name)
                .onTapGesture {
                    print($viewModel)
                }
            Spacer()
            TextField("name", text: $user.name)
        }
    }
}

The good news is that this works. However, the editing should take place in a chlid view.

Here's my adapted code. I get the correct behaviour (i.e. fruit name can be edited) when the EditView is not enclosed by a NavigationLink; howerver, when placed in NavigationLink, I'm back to the original, faulty behaviour (i.e. fruit name can't be edited).

import SwiftUI

struct Fruit: Identifiable {
    var id = UUID()
    var name: String
}

class ViewModel: ObservableObject {
    @Published var fruit: [Fruit] = [
        Fruit(name: "Apple"),
        Fruit(name: "Orange")
    ]
}

struct ContentView: View {
    @StateObject var viewModel = ViewModel()

    var body: some View {
        NavigationStack {
            List {
                // Note that we pass in a collection of our custom struct
                // and don't change the struct wholesale but rather a
                // property of it.
                ForEach($viewModel.fruit) { $fruit in
                    // In this case, the presence of a navigation link
                    // is causing the issue. Without this, we can edit
                    // as we would expect.
                    NavigationLink {
                        EditView(fruit: $fruit)
                    } label: {
                        Text("Label")
                    }
                }
            }
        }
    }
}

struct EditView: View {
    @Binding var fruit: Fruit

    var body: some View {
        TextField("Edit this fruit name", text: $fruit.name)
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

At the moment, it looks as though the NavigationLink itself might be causing the issue.

In the original code you were using the new NavigationStack but you were using the old NavigationLink(destination: , label: ) .

These are not designed to work with each other. Both NavigationLink(destination: , label: ) and NavigationView are deprecated. They are designed to work with each other.

If you are using NavigationStack then you should be using the new NavigationLink(value: , label: ) For more info see The SwiftUI cookbook for navigation - WWDC22 - Videos - Apple Developer

In the original code you were using the new NavigationStack but you were using the old NavigationLink(destination: , label: ) .

These are not designed to work with each other. Both NavigationLink(destination: , label: ) and NavigationView are deprecated. They are designed to work with each other.

If you are using NavigationStack then you should be using the new NavigationLink(value: , label: ) For more info see The SwiftUI cookbook for navigation - WWDC22 - Videos - Apple Developer